CFY-417 added error handler for 500 internal server errors
CFY-417 fixed a description message of the deployment's executions call's statuses parameter
CFY-417 fixed 500 internal server error bug when user tries to execute a workflow which doesn't exist in deployment
CFY-417 fixed 500 error message; it'll now be of correct format and also include the stack trace.
CFY-417 fix flake8 error
CFY-417 added a test for executing nonexisting workflow id
Merge branch 'develop' into feature/CFY-417-clear-error-message-for-internal-server-errors-in-manager-rest-server
CFY-417 fixed error code for nonexisting workflow to 400 from 404 (since it's not a resource in the REST sense); fixed internal server error 500 message including stacktrace
CFY-417 fixed exception name
Merge pull request #192 from CloudifySource/feature/CFY-417-clear-error-message-for-internal-server-errors-in-manager-rest-server

Feature/cfy 417 clear error message for internal server errors in manager rest server