Fix misspellings in heat

Fix misspellings detected by:
* pip install misspellings
* git ls-files | grep -v locale | misspellings -f -

Change-Id: I554143f00fe82154472e7eb6391291730dd3ddd4
Closes-Bug: #1257295
Closes-Bug: #1277515
Verify that parsed environment file maps to a dict

An internal unexpected exception is raised while create a stack with an
environment file which only has string content. We should handle the case
and raise the correct error message such as "The environment is not YAML
mapping".

Change-Id: Ie226d122593dd97c3607c269899c0743a9d917d3
Closes-Bug: #1273538
Remove TODO comments in create_resource

Since it's XML handling related and the ever having XML API intention
has been removed.

Change-Id: I7d7328f6d13caa861b7fc4b3fd22c4450b6097e5
Implement custom constraints

This adds a new registry of constraints and a CustomConstraint class to
be able to validate against external services.

blueprint param-constraints

Co-Authored-By: cedric.soulas@cloudwatt.com
Change-Id: Iffaf2c1179eaf5d88cdea02b63782cea9f3fc616
Merge "Implement custom constraints"
heat_keystoneclient add support to enable/disable domain users

Add support for enable/disable of stack domain users, so the
base class can gain suspend/resume support (required to migrate
User resource)

Change-Id: Ic2215620893ca8ab9b7f6f4b1362ced143f95009
blueprint: instance-users
Refactor SignalResponder to abstract user logic

Refactor to abstract the logic related to managing the user and
keypair, so in a future patch we can migrate to stack domain users.

Change-Id: Id112fdadcfa2cf1f47f00f93750110ec680a803e
blueprint: instance-users
Merge "Verify that parsed environment file maps to a dict"
Merge "Fix misspellings in heat"
Merge "Remove TODO comments in create_resource"
revert keystone client changes

Change-Id: I076babccbea682da7cc935dcdcba20d25c5fc62c