py3.7 fix

PyUnicode_AsUTF8() returns const char* in py3.7 instead of char*. Making
changes to reflect that which should also be safe in
other Python versions.

src/Tools/generateTemplates/templateClassPyExport.py

@@ -224,8 +224,8 @@ public:
     /// setter for special attributes (e.g. dynamic ones)
     /// Output: Success=1, Failure=-1, Ignore=0
     int setCustomAttributes(const char* attr, PyObject *obj);
-    PyObject *_getattr(char *attr);              // __getattr__ function
-    int _setattr(char *attr, PyObject *value);        // __setattr__ function
+    PyObject *_getattr(const char *attr);              // __getattr__ function
+    int _setattr(const char *attr, PyObject *value);        // __setattr__ function
 -
 
     /// getter for the object handled by this class
@@ -727,7 +727,7 @@ PyObject *@self.export.Name@::_repr(void)
 //--------------------------------------------------------------------------
 // @self.export.Name@ Attributes
 //--------------------------------------------------------------------------
-PyObject *@self.export.Name@::_getattr(char *attr)				// __getattr__ function: note only need to handle new state
+PyObject *@self.export.Name@::_getattr(const char *attr)			// __getattr__ function: note only need to handle new state
 {
     try {
         // getter method for special Attributes (e.g. dynamic ones)
@@ -795,7 +795,7 @@ PyObject *@self.export.Name@::_getattr(char *attr)				// __getattr__ function: n
     return @self.export.Father@::_getattr(attr);
 }
 
-int @self.export.Name@::_setattr(char *attr, PyObject *value) // __setattr__ function: note only need to handle new state
+int @self.export.Name@::_setattr(const char *attr, PyObject *value) // __setattr__ function: note only need to handle new state
 {
     try {
         // setter for  special Attributes (e.g. dynamic ones)