Added package py-versioneer (#15130)

* Added package py-versioneer

* Update python version

* Added python2 to versioneer

* Added python2 to versioneer

* Update var/spack/repos/builtin/packages/py-versioneer/package.py

Co-Authored-By: Adam J. Stewart <ajstewart426@gmail.com>

* Cleaning comments

* Removed temporarily @warner as a maintainer, waiting for answer

* Removed line

Co-authored-by: Adam J. Stewart <ajstewart426@gmail.com>

var/spack/repos/builtin/packages/py-versioneer/package.py

+# Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from spack import *
+
+
+class PyVersioneer(PythonPackage):
+    """Versioneer is a tool to automatically update version strings by
+    asking your version-control system about the current tree."""
+
+    homepage = "https://github.com/warner/python-versioneer"
+    url      = "https://github.com/warner/python-versioneer/archive/0.18.tar.gz"
+    git      = "https://github.com/warner/python-versioneer.git"
+
+    maintainers = ['scemama']
+
+    version('0.18', sha256='cf895b67f5bc62d61c4837458069ded8f66b4e5764c19f7253c51ee27e8b3a99')
+
+    depends_on('py-setuptools', type='build')