buildbot: list the failed dependencies in DescriptionDone

[mojca (Mojca Miklavec)]

I would find it useful if one could read the status/reason of failed dependency installation already in the generic output (like the waterfall view) rather than having to dig into details.

At the moment one only gets

install dependencies of gdal failed

I would prefer if this was more verbose. Perhaps something like:

• install foo's dependencies failed previously: bar baz (when failcache prevents starting any installation at all)
• install foo's dependency failed: bar (after the first dependency fails)
• install foo's dependencies failed with timeout (I see the timeout pretty often on 10.5 and I'm not sure what's causing it, but there might be other types of errors)

A similar trick is already used to produce the list of subports:

def extract_subportlist(rc, stdout, stderr):
    if rc != 0:
        # Set an empty subport list on error
        return {'subportlist': ''}
    subports = [x.strip() for x in stdout.splitlines()]
    return {'subportlist': ' '.join(sorted(subports))}

portwatcher_factory.addStep(SetPropertyFromCommandWithPortlist(
    command=util.WithProperties('./mpbb/mpbb list-subports %(fullportlist)s'),
    extract_fn=extract_subportlist,
    name='subports',
    description=['listing', 'subports']))

I guess that something similar could work here.

As a bonus I wouldn't mind if links to previously failed builds were auto generated on the same summary page.