WebAccess: workaround for Perl base64 padding
WebAccess: workaround for Perl base64 padding

* In the external_authentication_robot plugin, when using
  compressed assertions, if those are computed by a Perl
  script, Perl will not use padding in the base64 encoding.

  Python expects such padding, thus the padding is automatically
  added in case it is missing.

tiborsimko/invenio-access,tiborsimko/invenio-access,inveniosoftware/invenio-access,inveniosoftware/invenio-access