Add tests for comparing candidate and final versions in packaging (#11841).

This used to be buggy; Filip Gruszczyński contributed tests and a code
patch but the latter is not needed.

Lib/packaging/tests/test_version.py

@@ -101,8 +101,18 @@ class VersionTestCase(unittest.TestCase):
         True
         >>> V('1.2.0') >= V('1.2.3')
         False
+        >>> V('1.2.0rc1') >= V('1.2.0')
+        False
         >>> (V('1.0') > V('1.0b2'))
         True
+        >>> V('1.0') > V('1.0c2')
+        True
+        >>> V('1.0') > V('1.0rc2')
+        True
+        >>> V('1.0rc2') > V('1.0rc1')
+        True
+        >>> V('1.0c4') > V('1.0c1')
+        True
         >>> (V('1.0') > V('1.0c2') > V('1.0c1') > V('1.0b2') > V('1.0b1')
         ...  > V('1.0a2') > V('1.0a1'))
         True
@@ -129,6 +139,8 @@ class VersionTestCase(unittest.TestCase):
         ...  < V('1.0.dev18')
         ...  < V('1.0.dev456')
         ...  < V('1.0.dev1234')
+        ...  < V('1.0rc1')
+        ...  < V('1.0rc2')
         ...  < V('1.0')
         ...  < V('1.0.post456.dev623')  # development version of a post release
         ...  < V('1.0.post456'))