Disable pylint violation E0611 when importing assert_* methods from nose.tools

Cleaned up files with muliline imports

Cleaned up files that do not use these imports

Misread comment

common/djangoapps/static_replace/test/test_static_replace.py

@@ -1,6 +1,6 @@
 import re
 
-from nose.tools import assert_equals, assert_true, assert_false
+from nose.tools import assert_equals, assert_true, assert_false  # pylint: disable=E0611
 from static_replace import (replace_static_urls, replace_course_urls,
                             _url_replace_regex)
 from mock import patch, Mock