Fixed critical pylint warnings

Fixed the following pylint warnings:
   W0231
   W0621
   W0621

Change-Id: I6d49a19f843ab2b63740199ef387e7e878fa030f
Partial-Fixes: bug #1281164

mistral/api/controllers/v1/workbook.py

@@ -89,7 +89,7 @@ class WorkbooksController(rest.RestController):
     def get_all(self):
         LOG.debug("Fetch workbooks.")
 
-        workbooks = [Workbook.from_dict(values)
-                     for values in db_api.workbooks_get()]
+        workbooks_list = [Workbook.from_dict(values)
+                          for values in db_api.workbooks_get()]
 
-        return Workbooks(workbooks=workbooks)
+        return Workbooks(workbooks=workbooks_list)

mistral/context.py

@@ -90,16 +90,16 @@ def set_ctx(new_ctx):
     utils.set_thread_local(_CTX_THREAD_LOCAL_NAME, new_ctx)
 
 
-def _wrapper(ctx, thread_description, thread_group, func, *args, **kwargs):
+def _wrapper(context, thread_desc, thread_group, func, *args, **kwargs):
     try:
-        set_ctx(ctx)
+        set_ctx(context)
         func(*args, **kwargs)
     except Exception as e:
         LOG.exception("Thread '%s' fails with exception: '%s'"
-                      % (thread_description, e))
+                      % (thread_desc, e))
         if thread_group and not thread_group.exc:
             thread_group.exc = e
-            thread_group.failed_thread = thread_description
+            thread_group.failed_thread = thread_desc
     finally:
         if thread_group:
             thread_group._on_thread_exit()

mistral/dsl.py

@@ -54,7 +54,7 @@ class Parser(object):
     def get_tasks(self):
         tasks = self.doc.get("Workflow", {}).get("tasks", {})
 
-        for task_name, task_dsl in tasks.iteritems():
+        for _, task_dsl in tasks.iteritems():
             task_dsl["service_name"] = task_dsl["action"].split(':')[0]
             req = task_dsl.get("requires")
             if req and isinstance(req, list):

mistral/engine/scalable/executor/executor.py

@@ -52,7 +52,7 @@ def do_task_action(task):
     action.run()
 
 
-def handle_task_error(task, exc):
+def handle_task_error(task, exception):
     try:
         db_api.start_tx()
         try:

mistral/exceptions.py

@@ -37,12 +37,14 @@ class MistralException(ex.Error):
 
 class DataAccessException(MistralException):
     def __init__(self, message=None):
+        super(DataAccessException, self).__init__(message)
         if message:
             self.message = message
 
 
 class InvalidActionException(MistralException):
     def __init__(self, message=None):
+        super(InvalidActionException, self).__init__(message)
         if message:
             self.message = message
 
@@ -52,6 +54,7 @@ class DBDuplicateEntry(MistralException):
     code = "DB_DUPLICATE_ENTRY"
 
     def __init__(self, message=None):
+        super(DBDuplicateEntry, self).__init__(message)
         if message:
             self.message = message