py-cf-units: new package (#11891)

* py-cf-units: new package

* py-cf-units: download from pypi.io

* py-cf-units: include py-pytest-runner as build dep

* py-cf-units: remove empty build_args function

* py-cf-units: fix for flake8

* py-cf-units: indent docstring

* py-cf-units: remove excess spaces

* py-cf-units: list master branch ahead of numeric versions

* py-cf-units: remove extension keyword from version

var/spack/repos/builtin/packages/py-cf-units/package.py

+# Copyright 2013-2019 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 PyCfUnits(PythonPackage):
+    """Units of measure as required by the Climate and Forecast (CF)
+    metadata conventions.
+    """
+
+    homepage = "https://scitools.org.uk"
+    url      = "https://pypi.io/packages/source/c/cf-units/cf-units-2.1.1.tar.gz"
+    git      = "https://github.com/SciTools/cf-units.git"
+
+    version('master', branch='master')
+    version('2.1.1', sha256='fa0ef8efd84546e61088aa23e76ebbaf7043167dc3a7f35f34549c234b543530')
+
+    depends_on('python@3:', type=('build', 'run'))
+    depends_on('py-setuptools', type='build')
+    depends_on('py-six', type=('build', 'run'))
+    depends_on('py-cftime', type=('build', 'run'))
+    depends_on('py-cython', type=('build', 'run'))
+    depends_on('py-numpy', type=('build', 'run'))
+    depends_on('py-antlr4-python3-runtime', type=('build', 'run'))
+    depends_on('py-pytest-runner', type=('build'))
+    depends_on('udunits2')