Add a new logging BLATHER level to easily allow its
usage for messages that are below the normal DEBUG level
such as compilation information and scope lookup info
which can be very verbose in logs if always enabled.

Change-Id: I828211403bd02bfd6777b10cdcfe58fb0637a52c

When 'create_missing' is true the atom should be created
instead of raising an exception; this is used when a flow
detail is updated with a new detail and then saved.

This also adds test cases that verify this happens so that
we verify this on an ongoing basis.

Fixes bug 1395812

Change-Id: I4851a08ff1ab4101dbec4a6656177908095c3c52

Instead of copying modules from the incubator into taskflow
we can now directly use these same modules from supported
libraries instead so this moves the usage of everything except
uuidutils which wasn't moved over to using those newly published
libraries.

Part of blueprint integrate-and-use-oslo-utils-serialization

Change-Id: I1183bda96e1ddb062d9cab91990186f0f56f0a0e

To avoid the case where the transaction appears to have
committed successfully (when it actually has not) create
a new checked_commit utility function and use it in the
zookeeper persistence backend to ensure that the transaction
has completed correctly (when it has not raise a new kazoo
exception that contains the failures to the caller, which can
then reraise that exception, examine the failures or do some
other action).

Change-Id: Ib169b36abb568a0e1516c4c786fccb30856661e1

Update hacking to the new requirements version and
fix about half of the new reported issues. The other
hacking issues are for now ignored until fixed by
adjusting our tox.ini file.

This commit fixes the following new hacking errors:

H405 - multi line docstring summary not separated
       with an empty line
E265 - block comment should start with '# '
F402 - import 'endpoint' from line 21 shadowed by
       loop variable

Change-Id: I6bae61591fb988cc17fa79e21cb5f1508d22781c

- Convert the various functions that take a task detail into
  ones that take atom details (since this is now the generic
  type they should take).
- Don't expose the detail type strings as part of the atom
  detail api, leave those as private hidden strings and provide
  conversion functions from string<->class instead.
- Have the logbook objects contain the following new methods
  to reduce the dependence on persistence_utils to do the same.
  - to_dict() which converts the current object into a dict
  - from_dict() which converts the provided dict into a object
  - merge() which merges a incoming objects data with the current
    objects
- Have the persistence backends + storage + action engine use these
  new methods instead of there current usage.
- Don't compare to logbook.RETRY_DETAIL or logbook.TASK_DETAIL since
  python has the isinstance function just use it (ideally we should
  fix the code so that this isn't even needed, usage of isinstance
  means something is not designed/structured right).
- In storage tests we can't assume that failures will be non-lossy
  since under certain backends when a failure is stored information
  about the internally held exc_info is lost, so take this into
  account when testing by using matches() where applicable.

Change-Id: Ie8a274cfd4cb4e64e87c355dc99d466d74a4e82c

Group the exceptions into the following groups
  * Storage
  * Jobs
  * Execution
  * Other (wrapped failure here)

This grouping makes it easier to understand where
one type of exception should be used vs using another
type of exception.

Backwards incompatible changes:
  * StorageError -> StorageFailure
  * AlreadyExists -> Duplicate
  * WrappedFailure now inherits from Exception
    and not directly from TaskFlowException since it
    wraps arbitrary other exceptions and is not
    specific to taskflow.

Cleanups:
  * JobNotFound -> NotFound
  * EmptyFlow -> Empty
  * JobAlreadyExists -> AlreadyExists
  * InvariantViolation (X)
  * ConnectionFailure (X)

Change-Id: I0e1e81b513fbbc7adb8bfaa1244993e345ab70d3

Change-Id: I68082263189435af22d2bd6a63cc1ec77419668d

- Instead of formatting the exception by creating
  a storage error instance we can just let the already
  included cause make this formatting occur.
- Handle cases in impl_dir which were not catching and
  raising storage errors.
- Unify usage of 'backend internal error' messaging.
- Pass the cause to storage errors where applicable.

Change-Id: Ieb14256b202ccbfa3a96f68fa35db7e40f92114d