fix incorrect use of self.__class__ in super

[fmigneault]

Overview

Fix incorrect use of self.__class__ in super call.

Additional Information

In the actual context, it just so happens that self.__class__ is equal to ExecuteResponse and produces the same result.
When that class is derived though, to add additional functionalities, the value changes and causes endless recursion.

class DerivedExecuteResponse(ExecuteResponse): 
    def __init__(self, wps_request, uuid):
        super(ExecuteResponse, self).__init__(wps_request, uuid)
        # other setup... 

class ExecuteResponse(WPSResponse):
    def __init__(self, wps_request, uuid, **kwargs):
        # here 'self.__class__'  == 'DerivedExecuteResponse'
        # 'super(self.__class__, self)' resolves to 'ExecuteResponse', so it calls itself !
        super(self.__class__, self).__init__(wps_request, uuid)

Contribution Agreement

(as per https://github.com/geopython/pywps/blob/master/CONTRIBUTING.rst#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to PyWPS. I confirm that my contributions to PyWPS will be compatible with the PyWPS license guidelines at the time of contribution.
• I have already previously agreed to the PyWPS Contributions and Licensing Guidelines

[coveralls]

Coverage remained the same at 0.0% when pulling 4270724 on fmigneault:super-class into e10c99c on geopython:pywps-4.4.

[fmigneault]

@cehbrecht
Would be great if that can be integrated in #577
So far only found this problem while using 4.4, the rest seems to work correctly.

[cehbrecht]

@fmigneault Thanks for the fix 👍 I will update the release notes.