RawDataOutput does not work

[cehbrecht]

Description

I try to run an execute request with RawDataOutput but it ends with a server error.

Environment

• operating system:
• Python version:
• PyWPS version: 4.2.1
• source/distribution
  • [ ] git clone
  • [ ] Debian
  • [ ] PyPI
  • [ ] zip/tar.gz
  • [ ] other (please specify):
• web server
  • [ ] Apache/mod_wsgi
  • [ ] CGI
  • [ ] other (please specify):

Steps to Reproduce

Using wordcounter process of Emu.

Request: http://localhost:5000/wps?service=WPS&version=1.0.0&request=Execute&identifier=wordcounter&DataInputs=text=@xlink:href=https://cp4cds.github.io/&RawDataOutput=output

Error Message:

Traceback (most recent call last):
  File "/Users/pingu/.conda/envs/emu/lib/python3.6/site-packages/werkzeug/serving.py", line 270, in run_wsgi
    execute(self.server.app)
  File "/Users/pingu/.conda/envs/emu/lib/python3.6/site-packages/werkzeug/serving.py", line 258, in execute
    application_iter = app(environ, start_response)
  File "/Users/pingu/.conda/envs/emu/lib/python3.6/site-packages/werkzeug/wsgi.py", line 766, in __call__
    return self.app(environ, start_response)
  File "/Users/pingu/.conda/envs/emu/lib/python3.6/site-packages/werkzeug/wrappers.py", line 311, in application
    return resp(*args[-2:])
  File "/Users/pingu/.conda/envs/emu/lib/python3.6/site-packages/werkzeug/wrappers.py", line 308, in application
    resp = f(*args[:-2] + (request,))
  File "/Users/pingu/Documents/GitHub/birdhouse/pywps/pywps/response/execute.py", line 215, in __call__
    mimetype=self.wps_request.outputs[wps_output_identifier]['mimetype'])
KeyError: 'mimetype'

Additional Information