detecting version match/mismatch between core/plugins

[Wichmann, Mats D]

>This is going to look very ugly. It'd be better to at least try and
>import BzrNewError wouldn't it?
>
>>     else:
>>         warning('Bzrtools is not up to date with installed 
>bzr version'
>>                 ' %s. Please upgrade to bzrtools %i.%i.'
>>                 % (bzrlib.__version__, bzrlib_version[0],
>> bzrlib_version[1]))
>
>This could be a bit confusing if users are being asked to install a
>version which doesn't exist yet. Perhaps the warning should be more of
>a suggestion, ie. "There might a newer version available".

>From the beginning I was thinking of the way Firefox
extensions are handled - there's definitely interaction
with a registry site to answer these sorts of questions.
However for a plugin which *is* intended to be in
lockstep with bzr releases, it does seem reasonable
to spit out some sort of warning like the above.