I already managed to get the wizard window up, but when I make this call:

return self.env.ref('flota.action_resumen_report').report_action(self)
it give External ID flota.action_resumen_report
my xml report now is
<report
    id="action_resumen_report"
    string="Resumen de viajes"
    model="flota.resumen.viajes"
    report_type="qweb-pdf"
    name="flota.print_resumen_report"
    file="flota.print_resumen_report"
    menu="False"/>
<template id="print_resumen_report">
          <t t-call="web.html_container">
                <t t-foreach="docs" t-as="resumen_viajes">
                    <t t-call="web.external_layout">
                        <div class="page">
                    <div class="col-sm-6">
                        <table border="0" align="center" style="font-size:16pt;">
                            <tr >
                                 <td align="center" valign="center" colspan="6">
                                            RESUMEN DE LOS VIAJES
                                        </td>
                            </tr>
                            <tr><td colspan="6" style="height:10pt;"></td></tr>
                            <tr >
                                <td align="left" colspan="2">
                                    <label><strong>Año:</strong></label>
                                        <t t-esc="resumen_viajes.anno"/>
                                      <label>---</label>

                                            <label><strong>Mes:</strong></label>
                                        <t t-esc="resumen_viajes.mes"/>
                                    </td>
                                <td colspan="4"></td>
                                    </tr>

                            <tr>
                            <td valign="right" colspan="6">
                                <table class="table table-bordered mb32" style="table-layout:auto;font-size:14pt;">
                                    <tr>
                                        <td><strong>Centro de Costo</strong></td>
                                         <td colspan="3" align="center"><strong>Viajes Planificados</strong>
                                         </td>
                                        <td colspan="3" align="center"><strong>Viajes Imprevistos</strong>
                                        </td>
                                        <td ><strong>Viajes de Servicios </strong></td>
                                        <td ><strong>% Cumpl Transp. </strong></td>
                                    </tr>

                                    <tr > <td style="border-top:0;"></td>
                                                    <td><strong>Solicitados </strong></td>
                                                    <td><strong>Susp/Transp </strong></td>
                                                    <td><strong>Susp/Área </strong></td>

                                                    <td><strong>Solicitados </strong></td>
                                                    <td><strong>Susp/Transp </strong></td>
                                                    <td><strong>Susp/Área </strong></td>

                                        <td style="border-top:0;"></td>
                                        <td></td>
                                        </tr>
                                    <t t-foreach="resumen_viajes._get_Solicitudes()" t-as="centro_name">
                                    <tr colspan="2"><td > <div style="font-size:14pt;margin-bottom:5pt;" ><t t-esc="centro_name"/></div></td>


                                                    <td ><div style="font-size:14pt;" ><t t-esc="resumen_viajes._get_Total_SolicitudesP(centro_name)"/></div></td>
                                                    <td ><div style="font-size:14pt;" ><t t-esc="resumen_viajes._get_Total_Transporte_Plan(centro_name)"/></div></td>
                                                    <td > <div style="font-size:14pt;" ><t t-esc="resumen_viajes._get_Total_Area_Plan(centro_name)"/></div></td>


                                                    <td ><div style="font-size:14pt;" ><t t-esc="resumen_viajes._get_Total_SolicitudesI(centro_name)"/></div></td>
                                                    <td ><div style="font-size:14pt;" ><t t-esc="resumen_viajes._getTotal_Suspendidos_Transporte_Im(centro_name)"/></div></td>
                                                    <td ><div style="font-size:14pt;" ><t t-esc="resumen_viajes._getTotal_Suspendidos_Area_Im(centro_name)"/></div></td>

                                         <td > <div style="font-size:14pt;" ><t t-esc="resumen_viajes._get_Total_Solici_Serv(centro_name)"/></div></td>

                                        <td ><div style="font-size:14pt;" ><t t-esc="resumen_viajes._get_porciento(centro_name)"/></div></td>


                                    </tr>
                                        <tr>
                                    </tr>
                                  </t>
                                    <tr>
                                        <td><strong>Total</strong></td>
                                        <td><strong><t t-esc="resumen_viajes._get_Total_Final_SolicitudesP()" /></strong></td>
                                        <td><strong><t t-esc="resumen_viajes._get_Total_Final_Transporte_Plan()"/></strong></td>
                                        <td><strong><t t-esc="resumen_viajes._get_TotalFinal_Area_Plan()" /></strong></td>
                                        <td><strong><t t-esc="resumen_viajes._get_Total_Final_SolicitudesI()"/></strong></td>
                                        <td><strong><t t-esc="resumen_viajes._getTotal_Final_Suspendidos_Transporte_Im()"/></strong></td>
                                        <td><strong><t t-esc="resumen_viajes._getTotal_Final_Suspendidos_Area_Im()"/></strong></td>
                                        <td ><strong><t t-esc="resumen_viajes._get_Total_Final_Solici_Serv()"/> </strong></td>
                                        <td ><strong><t t-esc="resumen_viajes._get_Total_porciento()"/></strong></td>
                                    </tr>

                                </table>
                            </td>
                            </tr>
                        </table>
                    </div>
                </div>
                </t>
          </t>
          </t>
    </template>

</odoo>
my class py
class FlotaSolicitudResumenViajes(models.TransientModel):
    _name = 'flota.resumen.viajes'

    anno = fields.Char(string="Año", default=datetime.now().year, size=4)
    mes = fields.Selection([
        ('1', 'Enero'),
        ('2', 'Febrero'),
        ('3', 'Marzo'),
        ('4', 'Abril'),
        ('5', 'Mayo'),
        ('6', 'Junio'),
        ('7', 'Julio'),
        ('8', 'Agosto'),
        ('9', 'Septiembre'),
        ('10', 'Octubre'),
        ('11', 'Noviembre'),
        ('12', 'Diciembre')
    ], string='Mes', default=str(datetime.now().month))
def print_report(self):
    return self.env.ref('flota.action_resumen_report').report_action(self)
# RESUMEN DE VIAJES
@api.depends('anno', 'mes')
def _get_Solicitudes(self):
    centros_costo = []
    for record in self:
        sql_query = """Select centro_name from flota_solicitud where mes = """ + repr(
            record.mes) + " and anno = " + repr(record.anno) + " group by centro_name "
    self.env.cr.execute(sql_query, (record.id,))
    for c in self.env.cr.dictfetchall():
        centros_costo.append(c.get('centro_name'),
                             )

    return centros_costo

def _get_Total_Final_SolicitudesP(self):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('tipo_viaje', '=', 'planificado')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _get_Total_SolicitudesP(self, centro_name):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('centro_name', '=', centro_name),
            ('tipo_viaje', '=', 'planificado')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _get_Total_Area_Plan(self, centro_name):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('centro_name', '=', centro_name),
            ('tipo_viaje', '=', 'planificado'),
            ('causa', '=', 'area')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _get_TotalFinal_Area_Plan(self):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('tipo_viaje', '=', 'planificado'),
            ('causa', '=', 'area')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _get_Total_Transporte_Plan(self, centro_name):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('centro_name', '=', centro_name),
            ('tipo_viaje', '=', 'planificado'),
            ('causa', '=', 'transporte')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _get_Total_Final_Transporte_Plan(self):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('tipo_viaje', '=', 'planificado'),
            ('causa', '=', 'transporte')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _get_Total_Solici_Serv(self, centro_name):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('centro_name', '=', centro_name),
            ('tipo_viaje', '=', 'servicios'),
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _get_Total_Final_Solici_Serv(self):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('tipo_viaje', '=', 'servicios'),
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _get_Total_SolicitudesI(self, centro_name):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('centro_name', '=', centro_name),
            ('tipo_viaje', '=', 'imprevisto')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _get_Total_Final_SolicitudesI(self):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('tipo_viaje', '=', 'imprevisto')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _getTotal_Suspendidos_Area_Im(self, centro_name):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('centro_name', '=', centro_name),
            ('tipo_viaje', '=', 'imprevisto'),
            ('causa', '=', 'area')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _getTotal_Final_Suspendidos_Area_Im(self):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('tipo_viaje', '=', 'imprevisto'),
            ('causa', '=', 'area')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _getTotal_Suspendidos_Transporte_Im(self, centro_name):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('centro_name', '=', centro_name),
            ('tipo_viaje', '=', 'imprevisto'),
            ('causa', '=', 'transporte')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _getTotal_Final_Suspendidos_Transporte_Im(self):
    total = 0
    flota_solicitudes = self.env['flota.solicitud']
    for record in self:
        flota_solicitudes = flota_solicitudes | self.env['flota.solicitud'].search([
            ('anno', '=', record.anno),
            ('mes', '=', record.mes),
            ('tipo_viaje', '=', 'imprevisto'),
            ('causa', '=', 'transporte')
        ])
    for a in flota_solicitudes:
        total = total + 1
    return total

def _get_porciento(self, centro_name):
    total = 0
    total_transporte = 0
    causa = 'transporte'
    porciento_cumplimiento = 100

    for record in self:
        self._cr.execute("""Select * from flota_solicitud where mes = """ +
                         repr(record.mes) + " and anno = " + repr(record.anno) +
                         " and centro_name = " + repr(centro_name))
        data_total = self._cr.dictfetchall()
        for a in data_total:
            total += 1
        self._cr.execute("""Select * from flota_solicitud where mes = """ +
                         repr(record.mes) + " and anno = " + repr(record.anno) +
                         "and causa = " + repr(causa) +
                         " and centro_name = " + repr(centro_name))
        data_total_t = self._cr.dictfetchall()
        for a in data_total_t:
            total_transporte += 1
        if total_transporte != 0:
            porciento_cumplimiento = (total - total_transporte) / total * 100

    return round(porciento_cumplimiento, 2)

def _get_Total_porciento(self):
    total = 0
    total_transporte = 0
    causa = 'transporte'
    porciento_cumplimiento = 100

    for record in self:
        self._cr.execute("""Select * from flota_solicitud where mes = """ +
                         repr(record.mes) + " and anno = " + repr(record.anno))
        data_total = self._cr.dictfetchall()
        for a in data_total:
            total += 1
        self._cr.execute("""Select * from flota_solicitud where mes = """ +
                         repr(record.mes) + " and anno = " + repr(record.anno) +
                         "and causa = " + repr(causa))
        data_total_t = self._cr.dictfetchall()
        for a in data_total_t:
            total_transporte += 1
        if total_transporte != 0:
            porciento_cumplimiento = (total - total_transporte) / total * 100

    return round(porciento_cumplimiento, 2)




My views
<!--REPORTE PDF-->
     <record model="ir.ui.view" id="solicitud_resumen_form">
           <field name="name">flota.resumen.viajes.wizard</field>
            <field name="model">flota.resumen.viajes</field>
            <field name="arch" type="xml">
                <form string="Resumen de viajes" >
                        <group >
                            <field name="anno"  />
                            <field name="mes"  />
                        </group>
                    <footer>
                <button name="print_report" string="Generar" type="object" default_focus="1" class="oe_highlight"/>
                        or
                <button string="Cancel" class="btn btn-secondary" special="cancel" />
            </footer>
                </form>
            </field>
     </record>

         <act_window id="action_flota_resumen_viaje"
            name="Resumen de viajes PDF"
            res_model="flota.resumen.viajes"
            binding_model="flota.solicitud"
            binding_type="report"
            view_mode="form" target="new" />

thanks a lot for your cooperation!!!