Report missing bonds' types when using verbose flag (#486)

foyer/forcefield.py

@@ -348,11 +348,19 @@ def _error_or_warn(error, msg):
         warnings.warn(msg)
 
 
-def _check_bonds(data, structure, assert_bond_params):
+def _check_bonds(data, structure, verbose, assert_bond_params):
     """Check if any bonds lack paramters."""
     if data.bonds:
         missing = [b for b in structure.bonds if b.type is None]
         if missing:
+            if verbose:
+                for bond in missing:
+                    a1 = bond.atom1
+                    a2 = bond.atom2
+                    print(
+                        f"Missing bond with ids {(a1.idx, a2.idx)} and types "
+                        f"{[a1.type, a2.type]}."
+                    )
             nmissing = len(structure.bonds) - len(missing)
             msg = (
                 "Parameters have not been assigned to all bonds. "
@@ -859,7 +867,7 @@ def parametrize_system(
         if box_vectors is not None:
             structure.box_vectors = box_vectors
 
-        _check_bonds(data, structure, assert_bond_params)
+        _check_bonds(data, structure, verbose, assert_bond_params)
         _check_angles(data, structure, verbose, assert_angle_params)
         _check_dihedrals(
             data,