new package py-testpath (#13417)

* new package py-testpath

dependency of py-nbconvert

* py-testpath: fix flake8

* Remove the unnecessary pip dependency

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

@@ -0,0 +1,16 @@
+# 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 PyTestpath(PythonPackage):
+    """Testpath is a collection of utilities for Python code working with
+    files and commands."""
+
+    homepage = "https://github.com/jupyter/testpath"
+    url      = "https://pypi.io/packages/source/t/testpath/testpath-0.4.2.tar.gz"
+
+    version('0.4.2', sha256='b694b3d9288dbd81685c5d2e7140b81365d46c29f5db4bc659de5aa6b98780f8')