Python fastdispatch error message improvements

When overloaded C++ methods are called, the fastdispatch mode sometimes
optimises out the generation of the typecheck typemap code, resulting in
the 'Possible C/C++ prototypes' information not being in the error message.
Now when a TypeError is thrown, the exception message is modified to contain the
'Possible C/C++ prototypes'.

See issue #1293

Examples/test-suite/python/director_exception_runme.py

@@ -25,6 +25,13 @@ class MyFoo3(Foo):
     def ping(self):
         raise MyException("foo", "bar")
 
+class MyFoo4(Foo):
+
+    def ping(self, *args):
+        print(type("bad", "call")) # throws TypeError message: type() takes 1 or 3 arguments
+        return "Foo4.ping"
+
+
 # Check that the NotImplementedError raised by MyFoo.ping() is returned by
 # MyFoo.pong().
 ok = 0
@@ -51,7 +58,8 @@ b = launder(a)
 try:
     b.pong()
 except TypeError, e:
-    if str(e) == "SWIG director type mismatch in output value of type 'std::string'":
+    # fastdispatch mode adds on Additional Information to the exception message - just check the main exception message exists
+    if str(e).startswith("SWIG director type mismatch in output value of type 'std::string'"):
         ok = 1
     else:
         print "Unexpected error message: %s" % str(e)
@@ -74,6 +82,22 @@ except MyException, e:
 if not ok:
     raise RuntimeError
 
+
+# Check that the director returns the appropriate TypeError thrown in a director method
+ok = 0
+a = MyFoo4()
+b = launder(a)
+try:
+    b.pong()
+except TypeError as e:
+    if str(e).startswith("type() takes 1 or 3 arguments"):
+        ok = 1
+    else:
+        print "Unexpected error message: %s" % str(e)
+if not ok:
+    raise RuntimeError
+
+
 # This is expected to fail with -builtin option
 # Throwing builtin classes as exceptions not supported
 if not is_python_builtin():