[CTI] Relax formatting requirements for third bodies in reaction strings

Allow 'A + B (+M)' in addition to 'A + B (+ M)'

interfaces/cython/cantera/ctml_writer.py

@@ -403,6 +403,10 @@ def getReactionSpecies(s):
     >>> {'CH3':1, 'H':3.7, 'O2':5.2}
     """
 
+    # Normalize formatting of falloff third bodies so that there is always as
+    # space following the '+', e.g. '(+M)' -> '(+ M)'
+    s = s.replace(' (+', ' (+ ')
+
     # get rid of the '+' signs separating species. Only plus signs
     # surrounded by spaces are replaced, so that plus signs may be
     # used in species names (e.g. 'Ar3+')

interfaces/cython/cantera/test/test_convert.py

@@ -320,3 +320,7 @@ class CtmlConverterTest(utilities.CanteraTest):
         face = ct.Interface('diamond.cti', 'diamond_100', [gas, solid])
 
         self.assertNear(face.site_density, 3e-8)
+
+    def test_pdep(self):
+        gas = ct.Solution('../data/pdep-test.cti')
+        self.assertEqual(gas.n_reactions, 6)

test/data/pdep-test.cti

@@ -247,7 +247,7 @@ pdep_arrhenius('H + R4 <=> H + P4',
                [(10.0, 'atm'), 1.740000e+07, 1.98, 4521.0])
 
 # Reaction 5
-chebyshev_reaction('R5 + H (+ M) <=> P5A + P5B (+ M)',
+chebyshev_reaction('R5 + H (+ M) <=> P5A + P5B (+M)',
                    Tmin=300.0, Tmax=2000.0,
                    Pmin=(0.0098692326671601278, 'atm'), Pmax=(98.692326671601279, 'atm'),
                    coeffs=[[ 8.28830e+00, -1.13970e+00, -1.20590e-01,  1.60340e-02],