Remove three unused exceptions

These are never raised or extended.

Change-Id: Ia742bef6915b5ff6edd28bf4eb83c5f67b95eed1

tripleoclient/exceptions.py

@@ -21,10 +21,6 @@ class Base(Exception):
     """Base TripleO exception."""
 
 
-class Timeout(Base):
-    """An operation timed out"""
-
-
 class WorkflowServiceError(Base):
     """The service type is unknown"""
 
@@ -53,10 +49,6 @@ class PlanEnvWorkflowError(Base):
     """Plan Environment workflow has failed"""
 
 
-class StackInProgress(Base):
-    """Unable to deploy as the stack is busy"""
-
-
 class ConfigDownloadInProgress(Base):
     """Unable to deploy as config download already in progress"""
 
@@ -92,10 +84,6 @@ class NodeConfigurationError(WorkflowServiceError):
     """Node Configuration failed."""
 
 
-class StateTransitionFailed(Base):
-    """Ironic node state transition failed"""
-
-
 class ProfileMatchingError(Base):
     """Failed to validate or assign node profiles"""