sympy/sympy — pull request #1985 by skirpichev (2013-04-08 13:38:45+00:00)
Title: Fix exception while series expansion of function with multiple args

```
>>> zeta(x, y).series(y, 0, 2)
Traceback (most recent call last):
File "", line 1, in
File "/home/sk/sympy/py3k-sympy/sympy/core/expr.py", line 2360, in
series
s1 = self._eval_nseries(x, n=n, logx=None)
File "/home/sk/sympy/py3k-sympy/sympy/core/function.py", line 502, in
_eval_nseries
if (self.func.nargs == 1 and args0[0]) or self.func.nargs > 1:
TypeError: unorderable types: tuple() > int()
```

An example of this failure (python3 specific) is in PR #1977.