This is the error I got : 

Traceback (most recent call last):
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\tools\convert.py", line 741, in parse
    self._tags[rec.tag](rec, de, mode=mode)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\tools\convert.py", line 569, in _tag_record
    model = self.env[rec_model]
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\api.py", line 760, in __getitem__
    return self.registry[model_name]._browse((), self)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\modules\registry.py", line 177, in __getitem__
    return self.models[model_name]
KeyError: 'ir.actions.report.xml'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\http.py", line 648, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\http.py", line 309, in _handle_exception
    raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\tools\pycompat.py", line 86, in reraise
    raise value
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\http.py", line 685, in dispatch
    result = self._call_function(**self.params)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\http.py", line 341, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\service\model.py", line 97, in wrapper
    return f(dbname, *args, **kwargs)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\http.py", line 334, in checked_call
    result = self.endpoint(*a, **kw)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\http.py", line 929, in __call__
    return self.method(*args, **kw)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\http.py", line 514, in response_wrap
    response = f(*args, **kw)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\addons\web\controllers\main.py", line 920, in call_button
    action = self._call_kw(model, method, args, {})
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\addons\web\controllers\main.py", line 908, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\api.py", line 689, in call_kw
    return call_kw_multi(method, model, args, kwargs)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\api.py", line 680, in call_kw_multi
    result = method(recs, *args, **kwargs)
  File "<decorator-gen-39>", line 2, in button_immediate_install
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\addons\base\module\module.py", line 70, in check_and_log
    return method(self, *args, **kwargs)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\addons\base\module\module.py", line 437, in button_immediate_install
    return self._button_immediate_function(type(self).button_install)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\addons\base\module\module.py", line 530, in _button_immediate_function
    modules.registry.Registry.new(self._cr.dbname, update_module=True)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\modules\registry.py", line 84, in new
    odoo.modules.load_modules(registry._db, force_demo, status, update_module)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\modules\loading.py", line 341, in load_modules
    loaded_modules, update_module)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\modules\loading.py", line 240, in load_marked_modules
    loaded, processed = load_module_graph(cr, graph, progressdict, report=report, skip_modules=loaded_modules, perform_checks=perform_checks)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\modules\loading.py", line 156, in load_module_graph
    _load_data(cr, module_name, idref, mode, kind='data')
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\modules\loading.py", line 94, in _load_data
    tools.convert_file(cr, module_name, filename, idref, mode, noupdate, kind, report)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\tools\convert.py", line 788, in convert_file
    convert_xml_import(cr, module, fp, idref, mode, noupdate, report)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\tools\convert.py", line 849, in convert_xml_import
    obj.parse(doc.getroot(), mode=mode)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\tools\convert.py", line 738, in parse
    self.parse(rec, mode)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\tools\convert.py", line 748, in parse
    exc_info[2]
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\tools\pycompat.py", line 85, in reraise
    raise value.with_traceback(tb)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\tools\convert.py", line 741, in parse
    self._tags[rec.tag](rec, de, mode=mode)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\tools\convert.py", line 569, in _tag_record
    model = self.env[rec_model]
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\api.py", line 760, in __getitem__
    return self.registry[model_name]._browse((), self)
  File "C:\Program Files (x86)\Odoo 11.0\server\odoo\modules\registry.py", line 177, in __getitem__
    return self.models[model_name]
odoo.tools.convert.ParseError: "ir.actions.report.xml" while parsing file:/c:/program files (x86)/odoo 11.0/server/odoo/addons/oemaintenance/views/oemaintenance_reports.xml:29, near
<record id="oemaintenance.oemaintenance_monthly_task_report" model="ir.actions.report.xml">
            <field name="paperformat_id" ref="oemaintenance.paperformat_oemaintenance_monthly_report_task"/>
        </record>