tests: Add tests for imaputil.* functions

Add one test for each of the functions in offlineimap.imaputil, to make
sure they keep working. These functions tests the internal innards of
the offlineimap module rather than invoking offlineimap as a program.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

test/OLItest/TestRunner.py

@@ -24,10 +24,8 @@ import subprocess
 import tempfile
 import random
 random.seed()
-try:
-    from configparser import SafeConfigParser
-except ImportError: # python 2
-    from ConfigParser import SafeConfigParser
+
+from offlineimap.CustomConfig import CustomConfigParser
 from . import default_conf
 
 
@@ -75,7 +73,7 @@ class OLITestLib():
         #TODO, only do first time and cache then for subsequent calls?
         assert cls.cred_file != None
         assert cls.testdir != None
-        config = SafeConfigParser()
+        config = CustomConfigParser()
         config.readfp(default_conf)
         default_conf.seek(0) # rewind config_file to start
         config.read(cls.cred_file)