Raising NotImplementedError for some #TODO items, fixing units.

As discussed in #2321 (comment)
But maybe we just merge #2597
and rebase this onto that.

rmgpy/kinetics/surface.pyx

@@ -609,9 +609,11 @@ cdef class SurfaceArrhenius(Arrhenius):
  import cantera as ct
 
  A = self._A.value_si
+ raise NotImplementedError("The units need fixing from mol to kmol?")
+ # SEE https://github.com/ReactionMechanismGenerator/RMG-Py/pull/2597/
  b = self._n.value_si
  Ea = self._Ea.value_si * 1000 # convert from J/mol to J/kmol
-
+ raise NotImplementedError("Should return InterfaceArrheniusRate(A, b, E)? (and fix docstrings)")
  return ct.Arrhenius(A, b, Ea)