Move Python version checking to a separate module

Add a new module with methods for checking the Python version.

Instead of handling Python3 imports with try...except blocks, first
check the python version and then import the relevant modules.  This
makes the code a bit cleaner and will result in less diff when/if we
remove support for Python < 3 later.

Use the same mechanism to handle `input` vs. `raw_input` and add
suppression of pylint warnings caused by redefinition of the built-in
method `input`.

Change-Id: Ia403e525b88d77640a741ac50382146e7d635924
Also-by: Chirayu Desai <cdesai@cyanogenmod.org>
Signed-off-by: Chirayu Desai <cdesai@cyanogenmod.org>

subcmds/init.py

@@ -19,11 +19,11 @@ import platform
 import re
 import shutil
 import sys
-try:
-  # For python3
+
+from pyversion import is_python3
+if is_python3():
   import urllib.parse
-except ImportError:
-  # For python2
+else:
   import imp
   import urlparse
   urllib = imp.new_module('urllib')

subcmds/status.py

@@ -21,12 +21,13 @@ except ImportError:
   import dummy_threading as _threading
 
 import glob
-try:
-  # For python2
-  import StringIO as io
-except ImportError:
-  # For python3
+
+from pyversion import is_python3
+if is_python3():
   import io
+else:
+  import StringIO as io
+
 import itertools
 import os
 import sys

subcmds/sync.py

@@ -24,22 +24,17 @@ import socket
 import subprocess
 import sys
 import time
-try:
-  # For python3
+
+from pyversion import is_python3
+if is_python3():
   import urllib.parse
-except ImportError:
-  # For python2
+  import xmlrpc.client
+else:
   import imp
   import urlparse
+  import xmlrpclib
   urllib = imp.new_module('urllib')
   urllib.parse = urlparse
-try:
-  # For python3
-  import xmlrpc.client
-except ImportError:
-  # For python2
-  import imp
-  import xmlrpclib
   xmlrpc = imp.new_module('xmlrpc')
   xmlrpc.client = xmlrpclib
 

subcmds/upload.py

@@ -23,10 +23,11 @@ from editor import Editor
 from error import HookError, UploadError
 from project import RepoHook
 
-try:
+from pyversion import is_python3
+if not is_python3():
+  # pylint:disable=W0622
   input = raw_input
-except NameError:
-  pass
+  # pylint:enable=W0622
 
 UNUSUAL_COMMIT_THRESHOLD = 5