ttfonts.py: improve error message about bad psName
ttfonts.py: improve error message about bad psName

Distrotech/reportlab,Distrotech/reportlab,Distrotech/reportlab,kanarelo/reportlab,Distrotech/reportlab,kanarelo/reportlab,kanarelo/reportlab,Distrotech/reportlab,kanarelo/reportlab,kanarelo/reportlab