Raise an exception under Python < 3.4.

It also cleans up the README to remove references to Python 2
and removes Python 2-isms from the main config.

refs #5443

web/config.py

@@ -11,15 +11,11 @@
 #
 ##########################################################################
 
+import builtins
 import logging
 import os
 import sys
-import json
 
-if sys.version_info[0] >= 3:
-    import builtins
-else:
-    import __builtin__ as builtins
 
 # We need to include the root directory in sys.path to ensure that we can
 # find everything we need when running in the standalone runtime.
@@ -27,7 +23,7 @@ root = os.path.dirname(os.path.realpath(__file__))
 if sys.path[0] != root:
     sys.path.insert(0, root)
 
-from pgadmin.utils import env, IS_PY2, IS_WIN, fs_short_path
+from pgadmin.utils import env, IS_WIN, fs_short_path
 
 ##########################################################################
 # Application settings
@@ -566,15 +562,6 @@ try:
 except ImportError:
     pass
 
-
-# SUPPORT_SSH_TUNNEL can be override in local config file and if that
-# setting is False in local config then we should not check the Python version.
-if (SUPPORT_SSH_TUNNEL is True and
-    ((sys.version_info[0] == 2 and sys.version_info[1] < 7) or
-     (sys.version_info[0] == 3 and sys.version_info[1] < 4))):
-    SUPPORT_SSH_TUNNEL = False
-    ALLOW_SAVE_TUNNEL_PASSWORD = False
-
 # Disable USER_INACTIVITY_TIMEOUT when SERVER_MODE=False
 if not SERVER_MODE:
     USER_INACTIVITY_TIMEOUT = 0

web/pgAdmin4.py

@@ -11,13 +11,14 @@
 a webserver, this will provide the WSGI interface, otherwise, we're going
 to start a web server."""
 
-import os
+
 import sys
 
-if sys.version_info[0] >= 3:
-    import builtins
-else:
-    import __builtin__ as builtins
+if sys.version_info < (3, 4):
+    raise Exception('This application must be run under Python 3.4 or later.')
+
+import builtins
+import os
 
 # We need to include the root directory in sys.path to ensure that we can
 # find everything we need when running in the standalone runtime.

web/regression/runtests.py

@@ -24,10 +24,10 @@ import coverage
 
 import unittest
 
-if sys.version_info[0] >= 3:
-    import builtins
-else:
-    import __builtin__ as builtins
+if sys.version_info < (3, 4):
+    raise Exception('The test suite must be run under Python 3.4 or later.')
+
+import builtins
 
 # Ensure the global server mode is set.
 builtins.SERVER_MODE = None