Ensure exception provide the correct Content-Type

[gschwind]

Hello,

Because XML is 'text/*' we should set the charset in content type header
this the purpose of this changes.

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(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.
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[gschwind]

To pass unit test this patch series need #361

Best regards

[cehbrecht]

Looks reasonable.

[cehbrecht]

This PR removes get_headers method ... but it was not used anywhere.

[coveralls]

Coverage increased (+0.03%) to 73.094% when pulling 947c0f4 on gschwind:fix-001 into c9d46d6 on geopython:master.

[coveralls]

Coverage increased (+0.03%) to 73.094% when pulling 947c0f4 on gschwind:fix-001 into c9d46d6 on geopython:master.

[cehbrecht]

@gschwind: looks simple enough ... so I merge it. Thanks :)

[gschwind]

Hello,

The get_headers function was used because it overrides HTTPException.get_headers

Best regards