updated scheduler extension

[cehbrecht]

Overview

This PR updates the scheduler extension. It replaces dill by a json dump/load to transfer the job status to the scheduler working nodes.

It has been tested with slurm. See the updated scheduler docker demo: https://github.com/bird-house/birdhouse-docker-images/tree/master/pywps-scheduler-demo

Related Issue / Discussion

Additional Information

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

[cehbrecht]

@tommygod3 maybe you like to try it on your side. There are probably still issues which we can fix in this PR.

[coveralls]

Coverage increased (+0.6%) to 75.054% when pulling 3ddf237884d9d750e597bd5def7d3fd561f26b6a on cehbrecht:update-scheduler into e9b939aa1992c99cc151c86efed08b890096225a on geopython:master.

[tommygod3]

@cehbrecht Will have a look

[tommygod3]

@cehbrecht Tested on SLURM and it works :)

[cehbrecht]

@tommygod3 cool :) Thanks for trying it :)

[tommygod3]

Think it is safe to say this would close #480

[cehbrecht]

@tommygod3 done.