Gui: [skip ci] fix Gui.subgraphFromObject and improve error text if wrapping fails

src/Base/swigpyrun.cpp

@@ -24,6 +24,7 @@
 #include "PreCompiled.h"
 #include "PyExport.h"
 #include "Exception.h"
+#include <sstream>
 #if (defined(HAVE_SWIG) && (HAVE_SWIG == 1))
 #if defined(__clang__)
 # pragma clang diagnostic push

src/Base/swigpyrun.inl

@@ -29,8 +29,11 @@ int createSWIGPointerObj_T(const char* TypeName, void* obj, PyObject** ptr, int
 
     swig_type_info * swig_type = 0;
     swig_type = SWIG_TypeQuery(TypeName);
-    if (!swig_type)
-        throw Base::RuntimeError("Cannot find type information for requested type");
+    if (!swig_type) {
+        std::stringstream str;
+        str << "SWIG: Cannot find type information for requested type: " << TypeName;
+        throw Base::RuntimeError(str.str());
+    }
     
     *ptr = SWIG_NewPointerObj(obj,swig_type,own);
     if (*ptr == 0)