Log Message:
py-execnet: update to 1.5.0

1.5.0
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- support shell escaping in python pathnames of popen.

  Eugene Ciurana discovered that execnet breaks if you use
  pathnames with spaces in a "python=" part of a spec.
  We now use shlex.split to split the string.  There is a
  potential for regressions if you used quote or escape
  sequences as part of your python command.

- Only insert importdir into sys.path if it is not already in the path.

  This prevents a bug when using enum34 with python 3.6 and
  pytest-xdist.

  The issue is that enum34 installs an 'enum' module in site-packages
  which is normally shadowed by the stdlib version of enum, however in
  gateway_bootstrap.py site-packages is added at the front the the
  search path. This means on the workers enum34 is hit for import enum
  which in turn causes import re to fail (as it makes use of the new
  enum features in 3.6).

- fix 49 - use inspect.getfullargspec if possible to avoid deprecationwarnings

- fix 56 - use partials in safe_terminate to avoid a bad carried binding

- fix spec parsing on Windows due to path containing '\' characters.