Activate async test

[huard]

Overview

A unit test for asynchronous processes was not actually running asynchronously. The test now runs in async mode and will raise an error if it ever runs synchronously.

Related Issue / Discussion

In response to comments in #657

Additional Information

Depends on #663

Contribution Agreement

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

• [x] 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.
• [x] I have already previously agreed to the PyWPS Contributions and Licensing Guidelines

[coveralls]

Coverage increased (+0.3%) to 81.398% when pulling 06eee7d8fd966ef170922b4ed5e6d7b4cba6e54e on huard:activate_async_test into 85ca8191f1440e5906210408d2fa48c41f0ca679 on geopython:main.

[huard]

Done

[cehbrecht]

@huard thanks :)