Bind outside of the try block

If binding fails, we don't want to unbind
since there will be nothing bound, so do
the binding outside of the try/except
block to do this in the correct order.

Change-Id: Iebd3ea7a04265264043c47d4e943778538e8a153
Explicitly list the valid transitions to RESUMING state

Instead of having a catch-all in check_flow_transition
that handles valid transitions to the RESUMING state we
should just have an explicit mapping of which old_state to
RESUMING state is valid. This is much easier to examine and
reason about then having to determine which states the
catch-all will allow/be affected by.

Change-Id: I3a4226b17bf5ad8e5453a3ff6bc9078f7c24b520
Raise type error instead of silencing it

Instead of skipping the type error when invalid
configuration values are provided instead we should
just let the user know about these errors and let
said user handle them appropriatly (by not passing
in invalid configuration).

Change-Id: Id17258e5e06b47bcabd2bfd9d02b9d21181244be
Add stronger checking of backend configuration

Set a default if the backend configuration is not
provided as well as check for the configuration
being a dictionary instead of any arbitary non-false
type.

Change-Id: Id458ac0eb2d7b86c5602ed2f23a52fb2c6f6f0e7
Allow max_backoff and use count instead of attempts

Change-Id: I18f7e2a32b290dcc5b09c9c0c1fa098c47e477a7
Switch to just using tox

Instead of requiring all the complicated
venv management logic that tox already provides
just use tox directly instead. This maps more
closely to what jenkins does, and how most other
python development occurs (which does not typically
rely on custom venv scripts).

Change-Id: Iff6cf0a7eb24ddd2ef65ddd723d0e4cb803b9bb9
Fix spelling errors

Change-Id: I04b49b91be3031f246ede85d369525493f88be63
Merge "Explicitly list the valid transitions to RESUMING state"
Merge "Add stronger checking of backend configuration"
Merge "Allow max_backoff and use count instead of attempts"
Merge "Switch to just using tox"
Merge "Raise type error instead of silencing it"
Merge "Bind outside of the try block"
Merge "Fix spelling errors"