Python Flask AttributeError: 'Request' object has no attribute 'is_xhr'

#. Remove flask and install recent version

    pip uninstall flask
    pip intall flask


#. Else, go to your requirements.txt remove the verions of your plugins/libraries.
   ex: flask=0.12.0
          to
         flask


Re run the requriements.txt and make sure all it is now in updated version.
#before uninstall manually and run the below command.

pip install -r requirements.txt