New Package: py-astropy-helpers (#15658)

* [py-astropy-helpers] created template

* [py-astropy-helpers] - removed boilerplate - added homepage - added depends_on('py-astropy')

* [py-astropy-helpers] Setuptools versioning

* [py-astropy-helpers] cleaned up unused build_args method

* [py-astropy-helpers] py-astropy is a runtime dependency

* [py-astropy-helpers] requires python@3.6:

* [py-astropy-helpers] cleaned up unnecessary older versions

* [py-astropy-helpers] turns out py-astropy isn't actually a dependency

var/spack/repos/builtin/packages/py-astropy-helpers/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 PyAstropyHelpers(PythonPackage):
+    """The astropy-helpers package includes many build,
+    installation, and documentation-related tools used by the
+    Astropy project, but packaged separately for use by other
+    projects that wish to leverage this work."""
+
+    homepage = "https://github.com/astropy/astropy-helpers"
+    url      = "https://github.com/astropy/astropy-helpers/archive/v4.0.1.tar.gz"
+
+    version('4.0.1',  sha256='88602971c3b63d6aaa6074d013f995d1e234acb3d517d70d7fcebd30cdaf5c89')
+
+    depends_on('python@3.6:', type=('build', 'run'))
+    depends_on('py-setuptools@30.3:', type='build')