Ignore errors during cleanup of course export command.

lms/djangoapps/courseware/management/commands/export_course.py

@@ -72,7 +72,7 @@ def export_course_to_tarfile(course_key, filename):
         course_dir = export_course_to_directory(course_key, tmp_dir)
         compress_directory(course_dir, filename)
     finally:
-        shutil.rmtree(tmp_dir)
+        shutil.rmtree(tmp_dir, ignore_errors=True)
 
 
 def export_course_to_directory(course_key, root_dir):
@@ -83,7 +83,7 @@ def export_course_to_directory(course_key, root_dir):
         raise CommandError("Invalid course_id")
 
     # The safest characters are A-Z, a-z, 0-9, <underscore>, <period> and <hyphen>.
-    # We represent the first four with \w.  
+    # We represent the first four with \w.
     # TODO: Once we support courses with unicode characters, we will need to revisit this.
     replacement_char = u'-'
     course_dir = replacement_char.join([course.id.org, course.id.course, course.id.run])