buildbot.service: better handle error

fix for 2960

In case of 404, the buildbot.service was storing the 404 error instead of retrying next time

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>
Fix minor issue with the pylint Step:
 - indentation issue
 - don't write pylint additional log on a single line
Another attempt to fix the element does not exist (yet) problem.

Upon 404, we still define the object, with everything undefined, and register to events

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>
Merge pull request #1307 from delanne/PylintStep

Fix minor issue with the pylint Step
fix the watch of nextbuild existence

in case the build was already loaded, callback was never called with o == undefined

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>
Fix issue raised by benallard:
```
 1 Traceback (most recent call last):
 2   File "/home/benoit/buildbot/openvas/venv/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 577, in _runCallbacks
 3     current.result = callback(current.result, *args, **kw)
 4   File "/home/benoit/buildbot/openvas/venv/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 1155, in gotResult
 5     _inlineCallbacks(r, g, deferred)
 6   File "/home/benoit/buildbot/openvas/venv/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 1097, in _inlineCallbacks
 7     result = result.throwExceptionIntoGenerator(g)
 8   File "/home/benoit/buildbot/openvas/venv/local/lib/python2.7/site-packages/twisted/python/failure.py", line 389, in throwExceptionIntoGenerator
 9     return g.throw(self.type, self.value, self.tb)
10 --- <exception caught here> ---
11   File "/home/benoit/buildbot/buildbot/master/buildbot/process/buildstep.py", line 461, in startStep
12     results = yield self.run()
13   File "/home/benoit/buildbot/openvas/venv/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 1099, in _inlineCallbacks
14     result = g.send(result)
15   File "/home/benoit/buildbot/buildbot/master/buildbot/process/buildstep.py", line 576, in run
16     results = yield self._start_deferred
17   File "/home/benoit/buildbot/openvas/venv/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 577, in _runCallbacks
18     current.result = callback(current.result, *args, **kw)
19   File "/home/benoit/buildbot/buildbot/master/buildbot/process/buildstep.py", line 852, in <lambda>
20     d.addCallback(lambda res: self.createSummary(cmd.logs['stdio']))
21   File "/home/benoit/buildbot/buildbot/master/buildbot/steps/python.py", line 237, in createSummary
22     counts, summaries = self.counts, self.summaries
23 exceptions.AttributeError: 'PyLint' object has no attribute 'counts'
```
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Merge pull request #1308 from delanne/PylintStep

Fix issue raised by benallard
Merge pull request #1306 from tardyp/t2960

buildbot.service: better handle error

Fixes ticket:2960
Merge pull request #1309 from benallard/patch-1

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Show the builder description in the builder's web status page.
 - add builder's description in the DB
 - update builder.tpl.jade
Fix typo
 - Add migration unittest: test.unit.test_db_migrate_versions_039_add_builder_description
resultspec: treats None as smaller to anything

This avoids useless 500 when the data set contains
null datetimes
test for null datetime sorting
Refresh the First-run instructions.

- Move to pip
- Don't activate the virtualenv (IMO not necessary)
- Put less emphasis on docker.
- Remove the use of tail
- Refresh the logs (2011 and 2009 !)
- Explain a bit more what the commands are for.
more tests for resultsspec's nonecmp

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>
Merge pull request #1313 from tardyp/t2978

Fix: Loading the waterfall while a build is in progress return 500

Fixes ticket:2978
Update after review from Dustin.

- One sentence per line
- Restored the ``code-block``s
- language fix
Actually create two virtualenvs