global: unicode literals for config
global: unicode literals for config

* Forces unicode literals on config. (addresses #2967)

* PEP8/257 code style improvements.

Signed-off-by: Leonardo Rossi <5460ec99b71a72e7693c4088b5c2585e76e1c857@cern.ch>

tiborsimko/invenio-pidstore,inveniosoftware/invenio-pidstore,tiborsimko/invenio-pidstore,inveniosoftware/invenio-pidstore