Parser test: allow two different versions of an error message (#218).
Parser test: allow two different versions of an error message (#218).

We now allow both "Specification mandate value for attribute bearded.”
and "Specification mandates value for attribute bearded." since the
former is at least needed on Ubuntu 16.04 LTS and the latter on macOS
High Sierra.

hsorby/libcellml,libcellml/buildbot-testing,MichaelClerx/libcellml,MichaelClerx/libcellml,cellml/libcellml,cellml/libcellml,cellml/libcellml,hsorby/libcellml,MichaelClerx/libcellml,nickerso/libcellml,hsorby/libcellml,nickerso/libcellml,hsorby/libcellml,libcellml/buildbot-testing,cellml/libcellml,nickerso/libcellml,nickerso/libcellml