New package: py-gluoncv (#15856)

* [py-gluoncv] created template

* [py-gluoncv] added description and homepage

* [py-gluoncv] added dependencies

* [py-gluoncv] unicode in readme is causing build to fail

* [py-gluoncv] cleaned up fixmes

* [py-gluoncv] removed unnecessary python dependency listing

* [py-gluoncv] added cython

var/spack/repos/builtin/packages/py-gluoncv/no-unicode-readme.patch

@@ -0,0 +1,11 @@
+--- a/README.md	2020-04-03 11:56:41.820271316 -0400
++++ b/README.md	2020-04-03 11:56:55.901335611 -0400
+@@ -72,7 +72,7 @@
+ 
+ There are multiple versions of MXNet pre-built package available. Please refer to [mxnet packages](https://gluon-crash-course.mxnet.io/mxnet_packages.html) if you need more details about MXNet versions.
+ 
+-# Docs 📖
++# Docs
+ GluonCV documentation is available at [our website](https://gluon-cv.mxnet.io/index.html).
+ 
+ # Examples

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

@@ -0,0 +1,36 @@
+# 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 PyGluoncv(PythonPackage):
+    """GluonCV provides implementations of state-of-the-art
+    (SOTA) deep learning algorithms in computer vision. It aims
+    to help engineers, researchers, and students quickly
+    prototype products, validate new ideas and learn computer
+    vision."""
+
+    homepage = "https://gluon-cv.mxnet.io/"
+    url      = "https://github.com/dmlc/gluon-cv/archive/v0.6.0.tar.gz"
+
+    version('0.6.0', sha256='5ac89d73f34d02b2e60595a5cc35f46d0a69376567fae3a9518005dd89161305')
+
+    depends_on('py-setuptools',  type='build')
+    depends_on('py-numpy',       type=('build', 'run'))
+    depends_on('py-tqdm',        type=('build', 'run'))
+    depends_on('py-requests',    type=('build', 'run'))
+    depends_on('py-matplotlib',  type=('build', 'run'))
+    depends_on('py-portalocker', type=('build', 'run'))
+    depends_on('py-pillow',      type=('build', 'run'))
+    depends_on('py-scipy',       type=('build', 'run'))
+    depends_on('py-cython',      type='build')
+
+    patch('no-unicode-readme.patch')
+
+    def build_args(self, spec, prefix):
+        args = []
+        args.append('--with-cython')
+        return args