log out when a doc from the project collection is used

services/docstore/app/coffee/DocManager.coffee

@@ -16,6 +16,7 @@ module.exports = DocManager =
 					if docFromDocCollection?
 						return callback null, docFromDocCollection, mongoPath
 					else if doc?
+						logger.warn project_id:project_id, doc_id:doc_id, "doc just used from project collection, why?"
 						return callback null, doc, mongoPath
 					else
 						return callback new Errors.NotFoundError("No such doc: #{project_id}")

services/docstore/test/unit/coffee/DocManagerTests.coffee

@@ -11,7 +11,7 @@ describe "DocManager", ->
 	beforeEach ->
 		@DocManager = SandboxedModule.require modulePath, requires:
 			"./MongoManager": @MongoManager = {}
-			"logger-sharelatex": @logger = {log: sinon.stub()}
+			"logger-sharelatex": @logger = {log: sinon.stub(), warn:->}
 		@doc_id = ObjectId().toString()
 		@project_id = ObjectId().toString()
 		@callback = sinon.stub()