improve error message in _get_barycentric_coors()
improve error message in _get_barycentric_coors()

RexFuzzle/sfepy,vlukes/sfepy,lokik/sfepy,rc/sfepy,RexFuzzle/sfepy,lokik/sfepy,BubuLK/sfepy,sfepy/sfepy,RexFuzzle/sfepy,BubuLK/sfepy,BubuLK/sfepy,vlukes/sfepy,RexFuzzle/sfepy,sfepy/sfepy,lokik/sfepy,sfepy/sfepy,rc/sfepy,rc/sfepy,lokik/sfepy,vlukes/sfepy