Remove unittest2 in Python 2.7.

There's no reason to use it in Python 2.7:

* Everything that unittest2 adds is already present in Python 2.7.
* Older versions of unittest2 have a nasty bug whereby its base class does not
  call super(); this can result in some mix-in class's setUp()s not being
  called at all.
* It's no longer maintained.

Author: Roy Wellington Ⅳ

setup.py

@@ -8,9 +8,9 @@
 
 def getRequires():
     deps = ['smtpapi==0.1.3']
-    if sys.version_info < (3, 0):
+    if sys.version_info < (2, 7):
         deps.append('unittest2')
-    else:
+    elif (3, 0) <= sys.version_info:
         deps.append('unittest2py3k')
     return deps
 

test/__init__.py

@@ -1,5 +1,8 @@
 import os
-import unittest2 as unittest
+try:
+    import unittest2 as unittest
+except ImportError:
+    import unittest
 import json
 import sys
 try: