[test] Shorten prefix string in test_rql_role_with_unknown_vid
With Python3.7, this test fails as the error message returned by
rest_publish() is:
<p>an error occurred while interpreting this rql directive: ObjectNotFound('toto')</p>
while we previously assumed a comma after 'toto'.
Fixing this by only shortening the prefix used in out.startswith().
[MASTER]
load-plugins=cubicweb.pylintext
ignore=__pkginfo__
[MESSAGES CONTROL]
disable = too-many-ancestors,too-many-instance-attributes,too-many-public-methods,
too-few-public-methods,too-many-arguments,import-error
[BASIC]
function-rgx = [a-z_][a-z0-9_]{2,35}$
good-names=w,_
[TYPECHECK]
generated-members=debug,info,notice,warning,error,critical,exception
[CLASSES]
exclude-protected=_cw,_cnx,
# namedtuple public API.
_asdict,_fields,_replace,_source,_make
[FORMAT]
max-line-length=100
max-module-lines=2000