cubicweb-mercurial-server #2828366 workaround repo path handling in rulesets [validation pending]

Mercurial-server currently chokes on paths with spaces::

remote: Traceback (most recent call last):
remote: File "/usr/share/mercurial-server/hg-ssh", line 52, in <module>
remote: ruleset.rules.readfile(f)
remote: File "/usr/share/mercurial-server/mercurialserver/", line 80, in readfile
remote: rule([c.split("=", 1) for c in l[1:]])))
remote: File "/usr/share/mercurial-server/mercurialserver/", line 31, in rule
remote: matchers = [(k, globmatcher(v)) for k, v in pairs]
remote: ValueError: need more than 1 value to unpack
abort: no suitable response from remote hg!

This is a bit denial-of-service-ly.

done in0.2.1
load left0.000
closed by#3ac8c89f5b05 [schema,tests] enforce regex constraint on Repository title (closes #2828366)
patch[schema,tests] enforce regex constraint on Repository title (closes #2828366) [applied]