Fix misleading error message for E251

Here's my code snip:

```
    17  setup(
    18      name = 'cdiff',
    19      version = _meta['version'],
```

And the pep8 report:

```
~/ws/cdiff (master)$ pep8 --first --show-source setup.py 
setup.py:18:9: E251 no spaces around keyword / parameter equals
    name = 'cdiff',
        ^
```

I was very confused when reading the message, I think it is misleading and better to change the **"no"** to **"unexpected"** in the message.

BTW do you think we should allow the spaces around the equal sign in above case that one parameter takes the whole line?  I personally think that is more readable.