Add requests library to requirements.txt

Heat uses requests in a few places and is currently relying on the
python-*client dependencies to pull it in.  If the python-*client deps
stopped using requests, Heat would break.

Change-Id: Id1a0717836d2441dda33adfda3092d3004265f4a
Wrap api exceptions in _()

Change-Id: Ie9a60d919b3657ae23fe2f8c67d18d21f571af14
Partial-bug: #1199695
Wrap common exceptions in _()

Change-Id: Idb7aabc1dbabc0bbcb9b8b3892372059024c55c3
Partial-bug: #1199695
Convert str passed as Numbers/Integer to numbers

Previously, if a number-in-a-string was passed as a Number or Integer
property, it would be validated as correct but not be converted to
an integer (it's clear that the code intended to do this but had a trivial
bug).

Unfortunately, making this change causes some backwards incompatibility.

- Previously, an AllowedValues field could have strings in it, e.g.
  ['1', '3', '5'], and this would work if a string was passed as the
  real value.
- Resource code that relied on users accidentally passing strings
  instead of numbers will now break, since it will actually be
  receiving real numbers.

You can see evidence of this in the tests I had to update
elsewhere. I don't believe any existing Heat resources are affected
by this, but it is possible that there are some templates out there
that will break.

Change-Id: I879545cae5ca52f485803a8e172c5484f3920b67
Closes-bug: #1241276
Update openstack.common.db

This updates the openstack.common.db part of Oslo so it stops using
openstack.common.exception. The openstack.common.exception is now
deprecated and has been removed from oslo-incubator.

Change-Id: Ic6ef0e698e5060614859bc3894eb71524c8fce21
Stop using openstack.common.exception

The openstack.common.exception has been deprecated and removed from
oslo-incubator. Therefore, Heat should follow the recommendation and
stop the usage of this file altogether.

Change-Id: I0364da262d956cecea7b77ebc40ead8ece224828
Closes-Bug: #1208734
Merge "Add requests library to requirements.txt"
Merge "Update openstack.common.db"
Merge "Stop using openstack.common.exception"
Merge "Convert str passed as Numbers/Integer to numbers"
Merge "Wrap api exceptions in _()"
Merge "Wrap common exceptions in _()"