That is what is going wrong. ``lognorm_gen._pdf`` calls ``self._logpdf`` and ``gilbrat_gen._logpdf`` has one argument less than ``lognorm_gen._logpdf``.

An alternative fix is to change ``gilbrat_gen._pdf`` to:

    def _pdf(self, x):
        return exp(lognorm_gen._logpdf(x, 1.0))

Calling superclass methods like this is fragile though (hence this PR). If you both prefer the above then I'll change it to that solution.

Errors:

    ======================================================================
    ERROR: test_continuous_basic.test_cont_basic(<scipy.stats.distributions.gilbrat_gen object at 0xac55c0c>, (), 'gilbrat')
    ----------------------------------------------------------------------
    Traceback (most recent call last):
      File "/home/rgommers/.local/lib/python2.7/site-packages/nose/case.py", line 197, in runTest
        self.test(*self.arg)
      File "/home/rgommers/Code/scipy/scipy/stats/tests/test_continuous_basic.py", line 164, in wrap
        return func(*a, **kw)
      File "/home/rgommers/Code/scipy/scipy/stats/tests/test_continuous_basic.py", line 340, in check_pdf
        pdfv = distfn.pdf(median, *arg)
      File "/home/rgommers/Code/scipy/scipy/stats/distributions.py", line 1213, in pdf
        place(output,cond,self._pdf(*goodargs) / scale)
      File "/home/rgommers/Code/scipy/scipy/stats/distributions.py", line 4535, in _pdf
        return lognorm_gen._pdf(self, x, 1.0)
      File "/home/rgommers/Code/scipy/scipy/stats/distributions.py", line 4491, in _pdf
        return exp(self._logpdf(x, s))
    TypeError: _logpdf() takes exactly 2 arguments (3 given)

    ======================================================================
    ERROR: test_continuous_basic.test_cont_basic(<scipy.stats.distributions.gilbrat_gen object at 0xac55c0c>, (), 'gilbrat')
    ----------------------------------------------------------------------
    Traceback (most recent call last):
      File "/home/rgommers/.local/lib/python2.7/site-packages/nose/case.py", line 197, in runTest
        self.test(*self.arg)
      File "/home/rgommers/Code/scipy/scipy/stats/tests/test_continuous_basic.py", line 164, in wrap
        return func(*a, **kw)
      File "/home/rgommers/Code/scipy/scipy/stats/tests/test_continuous_basic.py", line 358, in check_pdf_logpdf
        pdf = distfn.pdf(vals, *args)
      File "/home/rgommers/Code/scipy/scipy/stats/distributions.py", line 1213, in pdf
        place(output,cond,self._pdf(*goodargs) / scale)
      File "/home/rgommers/Code/scipy/scipy/stats/distributions.py", line 4535, in _pdf
        return lognorm_gen._pdf(self, x, 1.0)
      File "/home/rgommers/Code/scipy/scipy/stats/distributions.py", line 4491, in _pdf
        return exp(self._logpdf(x, s))
    TypeError: _logpdf() takes exactly 2 arguments (3 given)

    ----------------------------------------------------------------------