Use 4.0 schema parser in 4 alpha and snapshot builds

Author: clohfink

cassandra/metadata.py

@@ -2770,7 +2770,7 @@ def export_as_string(self):
 
 def get_schema_parser(connection, server_version, timeout):
     version = Version(server_version)
-    if version >= Version('4.0.0'):
+    if version >= Version('4-a'):
         return SchemaParserV4(connection, timeout)
     if version >= Version('3.0.0'):
         return SchemaParserV3(connection, timeout)

tests/unit/test_util_types.py

@@ -267,6 +267,9 @@ def test_version_compare(self):
         self.assertTrue(Version('2.3.0.build0') > Version('2.3.0.1'))  # 4th part fallback to str cmp
         self.assertTrue(Version('2.3.0') < Version('2.3.0.build'))
 
+        self.assertTrue(Version('4-a') <= Version('4.0.0'))
+        self.assertTrue(Version('4-a') <= Version('4.0-alpha1'))
+        self.assertTrue(Version('4-a') <= Version('4.0-beta1'))
         self.assertTrue(Version('4.0.0') >= Version('4.0.0'))
         self.assertTrue(Version('4.0.0.421') >= Version('4.0.0'))
         self.assertTrue(Version('4.0.1') >= Version('4.0.0'))