[session] enforce coherency of login/passwd couple values when no anonymous user (closes: #1910849)
None may be returned for both if anonymous connection is not
allowed or if an empty login is used in configuration
Raise ConfigurationError is anonymous login is non-ascii (convention)
debian/tmp/usr/lib/PY_VERSION/site-packages/cubicweb/web usr/lib/PY_VERSION/site-packages/cubicweb
debian/tmp/usr/share/cubicweb/cubes/shared/data usr/share/cubicweb/cubes/shared
debian/tmp/usr/share/cubicweb/cubes/shared/wdoc usr/share/cubicweb/cubes/shared