Document BUILDBOT_TEST_DB_URL + provide example of using DB from Docker

[rutsky]

No description provided.

[rutsky]

TODO note at the end about not working MySQL 5.7 may be replaced with note that "MySQL 5.7 is currently unsupported, see issue #..." and appropriate issue on Buildbot bug tracker can be created.

[codecov-io]

Current coverage is 84.57%

Merging #1955 into master will not affect coverage as of 802605f

@@            master   #1955   diff @@
======================================
  Files          320     320       
  Stmts        31151   31151       
  Branches         0       0       
  Methods          0       0       
======================================
  Hit          26347   26347       
  Partial          0       0       
  Missed        4804    4804       

Review entire Coverage Diff as of 802605f

---

Uncovered Suggestions

1. +0.11% via ...ot/status/builder.py#381...414
2. +0.10% via ...ot/status/builder.py#453...481
3. +0.09% via ...dbot/changes/mail.py#478...505
4. See 7 more...

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[sa2ajj]

does not comply with one-sentence-per-line policy

[rutsky]

I checked section above for that style policy --- it doesn't follow it either :)
It's a good policy IMO. Fixed.

[sa2ajj]

We've been updating the docs to make it compliant. Not all of it is though :(

[sa2ajj]

I think an issue and a link to it is the way to go.

[rutsky]

I replaced TODO note with a link on http://trac.buildbot.net/ticket/3421.

[tardyp]

LGTM!

[rutsky]

@sa2ajj I resolved all stated issues, maybe merge?

[djmitche]

Yep, in fact BB's not compatible with 5.7 at all at the moment.