Added py-pybtex package (#4507)

* Added py-pybtex package

* added more dependencies to py-pybtex

* added run to py-latexcodec dependency

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

+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+
+from spack import *
+
+
+class PyPybtex(PythonPackage):
+    """Pybtex is a BibTeX-compatible bibliography processor written in
+       Python."""
+
+    homepage = "https://pybtex.org"
+    url      = "https://pypi.io/packages/source/P/Pybtex/pybtex-0.21.tar.gz"
+
+    version('0.21', 'e7b320b2bcb34c664c4385533a2ea831')
+
+    depends_on('py-setuptools', type='build')
+    depends_on('py-latexcodec@1.0.4:', type=('build', 'run'))
+    depends_on('py-pyyaml@3.01:', type=('build', 'run'))
+    depends_on('py-counter@1:', when='^python@:2.6', type=('build', 'run'))