Fix #11334: Cannot make multi-line code blocks in ipython

When codeop.compile_command() returns None it actually says "at least
some part of the code was compiled successfully" which is not really important
for checking if it's complete or not.
Once we haven't got any errors during compilation process, we just want
to check if there will be another nested block of code or not by checking
a colon.

IPython/core/inputtransformer2.py

@@ -636,7 +636,7 b' class TransformerManager:'
                 MemoryError, SyntaxWarning):
             return 'invalid', None
         else:
-            if res is None:
+            if not lines[-1].strip().endswith(':'):
                 return 'incomplete', find_last_indent(lines)
         return 'complete', None