pytest: add _pytest/_version.py and LICENSE

- pytest was not reporing the correct version from pytest.__version__.
  It reported 'unknown'

- this fixes issues on some systems where system-installed pytest plugins
  would try to use the version and convert it to an int

lib/spack/external/_pytest/LICENSE

+The MIT License (MIT)
+
+Copyright (c) 2004-2017 Holger Krekel and others
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

lib/spack/external/_pytest/_version.py

+# coding: utf-8
+# file generated by setuptools_scm
+# don't change, don't track in version control
+version = '3.2.5'

lib/spack/external/ordereddict_backport.py

@@ -24,7 +24,8 @@
 ##############################################################################
 """This file dispatches to the correct implementation of OrderedDict."""
 
-# TODO: this file can be removed when support for python 2.6 will be dropped
+# TODO: this file, along with py26/ordereddict.py, can be removed when
+# TODO: support for python 2.6 will be dropped
 
 # Removing this import will make python 2.6
 # fail on import of ordereddict

lib/spack/external/pytest.py

+# The MIT License (MIT)
+#
+# Copyright (c) 2004-2017 Holger Krekel and others
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy of
+# this software and associated documentation files (the "Software"), to deal in
+# the Software without restriction, including without limitation the rights to
+# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+# of the Software, and to permit persons to whom the Software is furnished to do
+# so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
 # PYTHON_ARGCOMPLETE_OK
 """
 pytest: unit and functional testing with Python.