[Cython] Direct log output to sys.stdout

This fixes the problem of some output (notably from the 1D solver)
going to std::cout when that is not the primary output location,
e.g. when using IDLE or the IPython QtConsole.

include/cantera/cython/wrappers.h

@@ -1,7 +1,10 @@
+#include "cantera/base/logger.h"
 #include "cantera/thermo/ThermoPhase.h"
 #include "cantera/transport/TransportBase.h"
 #include "cantera/kinetics/Kinetics.h"
 
+#include "Python.h"
+
 // Wrappers for preprocessor defines
 std::string get_cantera_version()
 {
@@ -13,6 +16,23 @@ int get_sundials_version()
     return SUNDIALS_VERSION;
 }
 
+class PythonLogger : public Cantera::Logger
+{
+public:
+    virtual void write(const std::string& s) {
+        // 1000 bytes is the maximum size permitted by PySys_WriteStdout
+        static const size_t N = 999;
+        for (size_t i = 0; i < s.size(); i+=N) {
+            PySys_WriteStdout("%s", s.substr(i, N).c_str());
+        }
+    }
+
+    virtual void error(const std::string& msg) {
+        std::string err = "raise Exception('''"+msg+"''')";
+        PyRun_SimpleString(err.c_str());
+    }
+};
+
 // Function which populates a 1D array
 #define ARRAY_FUNC(PREFIX, CLASS_NAME, FUNC_NAME) \
     void PREFIX ## _ ## FUNC_NAME(Cantera::CLASS_NAME* object, double* data) \

interfaces/cython/cantera/_cantera.pxd

@@ -505,6 +505,11 @@ cdef extern from "cantera/cython/wrappers.h":
     cdef string get_cantera_version()
     cdef int get_sundials_version()
 
+    cdef cppclass CxxPythonLogger "PythonLogger":
+        pass
+
+    cdef void CxxSetLogger "setLogger" (CxxPythonLogger*)
+
     # ThermoPhase composition
     cdef void thermo_getMassFractions(CxxThermoPhase*, double*) except +
     cdef void thermo_setMassFractions(CxxThermoPhase*, double*) except +

interfaces/cython/cantera/utils.pyx

@@ -1,6 +1,9 @@
 import sys
 cdef int _pythonMajorVersion = sys.version_info[0]
 
+cdef CxxPythonLogger* _logger = new CxxPythonLogger()
+CxxSetLogger(_logger)
+
 cdef string stringify(x):
     """ Converts Python strings to std::string. """
     # This method works with both Python 2.x and 3.x.