[1D] Throw an exception if transport state is inconsistent

The user can enable Soret (thermal) diffusion or multicomponent
transport in either order, but attempts to solve flame problems with
Soret enabled and the mixture-averaged transport approximation will
result in an error

include/cantera/oneD/StFlow.h

@@ -78,7 +78,12 @@ class StFlow : public Domain1D
     //! set the transport manager
     void setTransport(Transport& trans);
 
-    void enableSoret(bool withSoret);
+    //! Enable thermal diffusion, also known as Soret diffusion.
+    //! Requires that multicomponent transport properties be
+    //! enabled to carry out calculations.
+    void enableSoret(bool withSoret) {
+        m_do_soret = withSoret;
+    }
     bool withSoret() const {
         return m_do_soret;
     }

interfaces/cython/cantera/_cantera.pxd

@@ -748,7 +748,7 @@ cdef extern from "cantera/oneD/Sim1D.h":
         void setMaxGridPoints(int, size_t) except +translate_exception
         size_t maxGridPoints(size_t) except +translate_exception
         void setGridMin(int, double) except +translate_exception
-        void setFixedTemperature(double)
+        void setFixedTemperature(double) except +translate_exception
         void setInterrupt(CxxFunc1*) except +translate_exception
         void setTimeStepCallback(CxxFunc1*)
         void setSteadyCallback(CxxFunc1*)

src/oneD/StFlow.cpp

@@ -132,7 +132,7 @@ void StFlow::setupGrid(size_t n, const doublereal* z)
     }
 }
 
-void StFlow::resetBadValues(double* xg) 
+void StFlow::resetBadValues(double* xg)
 {
     double* x = xg + loc();
     for (size_t j = 0; j < m_points; j++) {
@@ -154,17 +154,6 @@ void StFlow::setTransport(Transport& trans)
     }
 }
 
-void StFlow::enableSoret(bool withSoret)
-{
-    if (m_do_multicomponent) {
-        m_do_soret = withSoret;
-    } else {
-        throw CanteraError("setTransport",
-                           "Thermal diffusion (the Soret effect) "
-                           "requires using a multicomponent transport model.");
-    }
-}
-
 void StFlow::_getInitialSoln(double* x)
 {
     for (size_t j = 0; j < m_points; j++) {
@@ -195,6 +184,12 @@ void StFlow::setGasAtMidpoint(const doublereal* x, size_t j)
 
 void StFlow::_finalize(const doublereal* x)
 {
+    if (!m_do_multicomponent && m_do_soret) {
+        throw CanteraError("_finalize",
+            "Thermal diffusion (the Soret effect) is enabled, and requires "
+            "using a multicomponent transport model.");
+    }
+
     size_t nz = m_zfix.size();
     bool e = m_do_energy[0];
     for (size_t j = 0; j < m_points; j++) {