Fix py2/3 imports of HTMLParser
Fix py2/3 imports of HTMLParser

tcmoore3/mbuild,summeraz/mbuild,ctk3b/mbuild,iModels/mbuild,summeraz/mbuild,sallai/mbuild,tcmoore3/mbuild,Jonestj1/mbuild,sallai/mbuild,iModels/mbuild,ctk3b/mbuild,Jonestj1/mbuild