V3000 parsing sets aromatic flags on bonds but not atoms. When removeHs
strips an explicit H from nitrogen in an aromatic ring, molRemoveH
checked heavyAtom->getIsAromatic() to decide whether to increment
numExplicitHs — but that flag was always false for V3000-parsed atoms.
Without the explicit H count, the kekulizer cannot distinguish pyrrole N from pyridine N,
causing
"Can't kekulize mol" errors on valid ChemDraw-exported molblocks.
Fix: use isAromaticAtom(), which checks both atom and bond aromatic
flags
1a3cc2d5e8