Replace pkg_resources.parse_version with packaging.version.parse

This is a step towards removing the dependency on pkg_resources, which is part
of setuptools, and thus makes setuptools a runtime dependency.

gunicorn/workers/geventlet.py

@@ -11,7 +11,7 @@ try:
 except ImportError:
     raise RuntimeError("eventlet worker requires eventlet 0.24.1 or higher")
 else:
-    from pkg_resources import parse_version
+    from packaging.version import parse as parse_version
     if parse_version(eventlet.__version__) < parse_version('0.24.1'):
         raise RuntimeError("eventlet worker requires eventlet 0.24.1 or higher")
 

gunicorn/workers/ggevent.py

@@ -14,7 +14,7 @@ try:
 except ImportError:
     raise RuntimeError("gevent worker requires gevent 1.4 or higher")
 else:
-    from pkg_resources import parse_version
+    from packaging.version import parse as parse_version
     if parse_version(gevent.__version__) < parse_version('1.4'):
         raise RuntimeError("gevent worker requires gevent 1.4 or higher")
 

setup.py

@@ -75,6 +75,7 @@ install_requires = [
     # is the first version to support Python 3.4 which we require as a
     # floor.
     'setuptools>=3.0',
+    'packaging',
 ]
 
 extras_require = {