Tidy Dep_server.calc_direct_dependents_utils
Tidy Dep_server.calc_direct_dependents_utils

Summary:
* use local open and dedent
* fix comment indentation
* rename 'b' to 'is_path_dependent_file'
* change (a, (b, c)) to (a, b, c)

Reviewed By: gkz

Differential Revision: D22861903

fbshipit-source-id: cdb7849557a4fd17743ba8d6a88350cee5881fa8

nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow