Fix the license entry in the setup file

PyGreSQL is licensed under the PostgreSQL license (see LICENSE.txt)
and not the Python Software Foundation license.

LICENSE.txt

@@ -9,6 +9,9 @@ Further modifications copyright (c) 1997-2008 by D'Arcy J.M. Cain
 
 Further modifications copyright (c) 2009-2017 by the PyGreSQL team.
 
+PyGreSQL is released under the PostgreSQL License, a liberal Open Source
+license, similar to the BSD or MIT licenses:
+
 Permission to use, copy, modify, and distribute this software and its
 documentation for any purpose, without fee, and without a written agreement
 is hereby granted, provided that the above copyright notice and this

setup.py

@@ -180,7 +180,7 @@ def finalize_options(self):
     url="http://www.pygresql.org",
     download_url="http://www.pygresql.org/download/",
     platforms=["any"],
-    license="Python",
+    license="PostgreSQL",
     py_modules=py_modules,
     ext_modules=[Extension('_pg', c_sources,
         include_dirs=include_dirs, library_dirs=library_dirs,
@@ -192,7 +192,7 @@ def finalize_options(self):
     classifiers=[
         "Development Status :: 6 - Mature",
         "Intended Audience :: Developers",
-        "License :: OSI Approved :: Python Software Foundation License",
+        "License :: OSI Approved :: The PostgreSQL License",
         "Operating System :: OS Independent",
         "Programming Language :: C",
         'Programming Language :: Python',