Add recognition of Conda virtual environments

[ibebio]

Hi,
we used Conda virtual environments instead of virtualenv and ran into the issue that toil does not recognize that it is running inside a Conda virtual environment. _toil_worker could thus not be found, without explicitely setting the PATH variable to point to its location in .bash_profile.

Extending the check for virtual environments inVirtualEnv() in src/toil/init.py to
return hasattr(sys, 'real_prefix') or 'CONDA_DEFAULT_ENV' in os.environ
solved the problem for us. Would this change make sense, and should I submit a pull request?

Thanks, Ilja

┆Issue is synchronized with this JIRA Story
┆Issue Number: TOIL-377

[DailyDreaming]

@ibebio Yes, that sounds like a sensible change. Please do submit a PR! Thanks for posting this. :)