GitLab

- Add custom exception for entity not being found
- Raise new exception when DN cannot be found from search
- Fix fetch method to return empty group object when search brings back
  no results, but preserve exception raise for multiple failed searches

* Refactor MCommGroup.fetch(), mainly to reduce nesting.

* Centralize defaulting of list attrs to []; the old code was both
  overly duplicated and failed to account for some situations.

* Most LDAP attributes are not case sensitive, but we were doing a
  case-sensitive check for the umichGroup object class.

* Group display name matching was only casefolding one side of the
  comparison.

This reverts merge request !4

* Refactor MCommGroup.fetch(), mainly to reduce nesting.

* Centralize defaulting of list attrs to []; the old code was both
  overly duplicated and failed to account for some situations.

* Most LDAP attributes are not case sensitive, but we were doing a
  case-sensitive check for the umichGroup object class.

* Group display name matching was only casefolding one side of the
  comparison.