Replace all clean_course_id form methods with common method.

cms/djangoapps/contentstore/config/forms.py

@@ -4,13 +4,13 @@ Defines a form for providing validation.
 import logging
 
 from django import forms
+from opaque_keys import InvalidKeyError
+from opaque_keys.edx.locator import CourseLocator
+from six import text_type
 
 from contentstore.config.models import CourseNewAssetsPageFlag
-
-from opaque_keys import InvalidKeyError
-from six import text_type
+from openedx.core.lib.courses import clean_course_id
 from xmodule.modulestore.django import modulestore
-from opaque_keys.edx.locator import CourseLocator
 
 log = logging.getLogger(__name__)
 
@@ -23,16 +23,7 @@ class CourseNewAssetsPageAdminForm(forms.ModelForm):
         fields = '__all__'
 
     def clean_course_id(self):
-        """Validate the course id"""
-        cleaned_id = self.cleaned_data["course_id"]
-        try:
-            course_key = CourseLocator.from_string(cleaned_id)
-        except InvalidKeyError:
-            msg = u'Course id invalid. Entered course id was: "{0}."'.format(cleaned_id)
-            raise forms.ValidationError(msg)
-
-        if not modulestore().has_course(course_key):
-            msg = u'Course not found. Entered course id was: "{0}". '.format(text_type(course_key))
-            raise forms.ValidationError(msg)
-
-        return course_key
+        """
+        Validate the course id
+        """
+        return clean_course_id(self)