Adding tests for #27467 surfaced some bugs:
from pandas import *
df = DataFrame(dict(a=[0, 0, 0, 1, 1, 1], b=range(6)))
g = df.groupby(np.repeat([0,1], 3))
# ok
g.quantile(50)
<segfault>
quantile accepts floats in [0,1] or arrays of floats. It appears not to validate the range though.
