py-threadpoolctl: add new package (#16606)

var/spack/repos/builtin/packages/py-threadpoolctl/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)
+
+
+class PyThreadpoolctl(PythonPackage):
+    """Python helpers to limit the number of threads used in the
+    threadpool-backed of common native libraries used for scientific
+    computing and data science (e.g. BLAS and OpenMP)."""
+
+    homepage = "https://github.com/joblib/threadpoolctl"
+    url      = "https://pypi.io/packages/source/t/threadpoolctl/threadpoolctl-2.0.0.tar.gz"
+
+    import_modules = ['threadpoolctl']
+
+    version('2.0.0', sha256='48b3e3e9ee079d6b5295c65cbe255b36a3026afc6dde3fb49c085cd0c004bbcf')
+
+    depends_on('python@3.5:', type=('build', 'run'))