[sources] Skip problematic sources when starting shell instead of crashing. Closes #3670208 At least this gives an opportunity to fix the problem in using c-c shell, which is currently not possible because it crashes during initialization. Notice that since sources are copy based, it should not be a problem at all to have some disabled, beside for services such as authentication sources as ldapfeed.

\.svn
^build$
^dist$
\.pyc$
\.pyo$
\.bak$
\.old$
\~$
\#.*?\#$
\.swp$
^doc/book/en/apidoc$
\.old$
syntax: regexp
.*/data/database/.*\.sqlite
.*/data/database/.*\.config
.*/data/database/tmpdb.*
.*/data/ldapdb/.*
^doc/html/
^doc/doctrees/
^doc/book/en/devweb/js_api/
data/pgdb/