Minor wxPython scripting improvements.

* Wrap Pgm().OnPgmExit() changes in APP_SINGLE_TOP to build conditionally
  when KICAD_SCRIPTING_WXPYTHON is enabled.
* Check the result of loading the correct wxPython version during
  initialization.

common/single_top.cpp

@@ -143,8 +143,10 @@ struct APP_SINGLE_TOP : public wxApp
 
     int  OnExit()           // overload wxApp virtual
     {
+        // Fixes segfault when wxPython scripting is enabled.
+#if defined( KICAD_SCRIPTING_WXPYTHON )
         Pgm().OnPgmExit();
-
+#endif
         return wxApp::OnExit();
     }
 
@@ -171,6 +173,11 @@ struct APP_SINGLE_TOP : public wxApp
             wxLogError( wxT( "Unhandled exception of unknown type" ) );
         }
 
+        // Works properly when wxPython scripting is disabled.
+#if !defined( KICAD_SCRIPTING_WXPYTHON )
+        Pgm().OnPgmExit();
+#endif
+
         return ret;
     }
 
@@ -281,8 +288,9 @@ bool PGM_SINGLE_TOP::OnPgmInit( wxApp* aWxApp )
             // We've already initialized things at this point, but wx won't call OnExit if
             // we fail out. Call our own cleanup routine here to ensure the relevant resources
             // are freed at the right time (if they aren't, segfaults will occur).
+#if defined( KICAD_SCRIPTING_WXPYTHON )
             OnPgmExit();
-
+#endif
             // Fail the process startup if the file could not be opened,
             // although this is an optional choice, one that can be reversed
             // also in the KIFACE specific OpenProjectFiles() return value.

scripting/python_scripting.cpp

@@ -145,7 +145,16 @@ bool pcbnewInitPythonScripting( const char * aUserPluginsPath )
     // are different versions of wxPython installed this can lead to select wrong wxPython
     // version being selected.
     snprintf( cmd, sizeof(cmd), "import wxversion; wxversion.select('%s')", WXPYTHON_VERSION );
-    PyRun_SimpleString( cmd );
+
+    int retv = PyRun_SimpleString( cmd );
+
+    if( retv != 0 )
+    {
+        wxLogError( wxT( "Python error %d occurred running string `%s`" ), retv, cmd );
+        PyErr_Print();
+        Py_Finalize();
+        return false;
+    }
 
     // Load the wxPython core API.  Imports the wx._core_ module and sets a
     // local pointer to a function table located there.  The pointer is used