Limit pyOpenSSL version

[Glutexo]

The pyOpenSSL package currently required does not support Python 2.6 in its most recent version 18.0.0. However only a one step previous version 17.5.0 still supports it and installs just fine.

We should note this specific version in the dependency list. Otherwise the package is not installable on systems with this legacy version of Python (RHEL 6). We must make it only an upper limit though, because pyOpenSSL installed from an RPM on RHEL 6 is of version 0.13.1. Limiting to an exact version would force installing one from PIP and rewriting the one from RPM.

Update:

pyOpenSSL requires pycparser, which dropped support for Python 2.6 a few days ago. It’s necessary to limit this to version <=2.18, otherwise pyOpenSSL would not install.