Mock server raises key error for validate_token

[Michael Nelson]

Just a minor difference between the mock server and the real one:

If validate_token is called with an unknown token, the real service returns False, whereas the mockservice raises a key error.

[Michael Nelson (michael.nelson)]

Hrm... I went to create a branch and fix this, but there are issues when setting up the dev environment (looks like the distribution of lazr.restful==0.9.17 is no longer where it was expected):

{{{
Downloading/unpacking lazr.restful==0.9.17 (from -r requirements.txt (line 16))
  Could not find a version that satisfies the requirement lazr.restful==0.9.17 (from -r requirements.txt (line 16)) (from versions: )
No distributions matching the version for lazr.restful==0.9.17 (from -r requirements.txt (line 16))
Storing complete log in /home/michael/.pip/pip.log
}}}

and pip.log with details: https://pastebin.canonical.com/35122/