Fix `return` in `except`

[kichik]

The following code tries to return a value from an except block but fails with an assertion.

import meta

def f(x):
    try:
        return x
    except:
        return x + 1  # <== offender

f_ast = meta.decompiler.decompile_func(f)
meta.asttools.print_ast(f_ast)
print meta.dump_python_source(f_ast)

It results in the following assertion:

AssertionError:              21 RETURN_VALUE

The suggested patch simply adds support for return and seems to work. It results in valid AST.

[stuaxo]

Hi @srossross any chance of merging this ?