fix version detection

shadowsocks/utils.py

@@ -39,10 +39,10 @@ def check_python():
     if info[0] == 2 and not info[1] >= 6:
         print('Python 2.6+ required')
         sys.exit(1)
-    if info[0] == 3 and not info[1] >= 3:
+    elif info[0] == 3 and not info[1] >= 3:
         print('Python 3.3+ required')
         sys.exit(1)
-    else:
+    elif info[0] not in [2, 3]:
         print('Python version not supported')
         sys.exit(1)