closes 109 - fix safe file handling in unit tests

[jachym]

Overview

fixes #109

Additional Information

introducing private _stream attribute for IOHandler class - so we can keep track on open files

Contribution Agreement

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

• I have already previously agreed to the PyWPS Contributions and Licensing Guidelines

[coveralls]

Coverage increased (+0.04%) to 76.635% when pulling 6d2937a on jachym:109_close_stream into 31c7b14 on geopython:master.

[coveralls]

Coverage increased (+0.04%) to 76.635% when pulling 6d2937a on jachym:109_close_stream into 31c7b14 on geopython:master.