python: Add 'long_description' to 'setup.py'.

This means we get a nicer description on pypi.org [1]. See [2] for more
info.

[1] https://pypi.org/project/ovs/
[2] https://packaging.python.org/en/latest/guides/making-a-pypi-friendly-readme/

Signed-off-by: Stephen Finucane <stephen@that.guru>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

python/setup.py.template

@@ -25,6 +25,9 @@ except ImportError:  # Needed for setuptools < 59.0
 import setuptools
 
 VERSION = "@VERSION@"
+README_PATH = os.path.abspath(
+    os.path.join(os.path.abspath(__file__), os.pardir, 'README.rst')
+)
 
 for x in ("version.py", "dirs.py"):
     if not os.path.exists(f"ovs/{x}"):
@@ -32,6 +35,9 @@ for x in ("version.py", "dirs.py"):
               file=sys.stderr)
         sys.exit(-1)
 
+with open(README_PATH) as fh:
+    long_description = fh.read()
+
 ext_errors = (CCompilerError, ExecError, PlatformError)
 if sys.platform == 'win32':
     ext_errors += (IOError, ValueError)
@@ -75,6 +81,8 @@ flow_extras_require = ['netaddr', 'pyparsing']
 setup_args = dict(
     name='ovs',
     description='Open vSwitch library',
+    long_description=long_description,
+    long_description_content_type='text/x-rst',
     version=VERSION,
     url='http://www.openvswitch.org/',
     author='Open vSwitch',