```
>>> re.sub('a*', '-', 'a')
'--'
>>> re.sub('a*', '-', 'aa')
'--'
>>> re.sub('a*', '-', 'aaa')
'--'
```

Shouldn't it be returning one dash, not two, since the greedy quantifier will match all the a's? I understand why substituting on 'b' returns '-a-', but shouldn't this constitute only one match? In Python 2.7, it behaves as I expect:

```
>>> re.sub('a*', '-', 'a')
'-'
>>> re.sub('a*', '-', 'aa')
'-'
>>> re.sub('a*', '-', 'aaa')
'-'
```

The original case that led me to this was trying to normalize a path to end in one slash. I used `re.sub('/*$', '/', path)`, but a nonzero number of slashes came out as two.