Cannot run tests on HEAD due to `object.__init__() takes no parameters` on `BaseOffset.__init__(self, n, normalize)`

[tswast]

Code Sample, a copy-pastable example if possible

$ pytest pandas/tests/io/test_gbq.py

During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/Users/swast/.pyenv/versions/3.6.4/envs/pandas-HEAD/lib/python3.6/site-packages/_pytest/config/__init__.py", line 406, in _importconftest
    mod = conftestpath.pyimport()
  File "/Users/swast/.pyenv/versions/3.6.4/envs/pandas-HEAD/lib/python3.6/site-packages/py/_path/local.py", line 668, in pyimport
    __import__(modname)
  File "/Users/swast/src/pandas/pandas/pandas/__init__.py", line 42, in <module>
    from pandas.core.api import *
  File "/Users/swast/src/pandas/pandas/pandas/core/api.py", line 10, in <module>
    from pandas.core.groupby.groupby import Grouper
  File "/Users/swast/src/pandas/pandas/pandas/core/groupby/__init__.py", line 2, in <module>
    from pandas.core.groupby.groupby import (
  File "/Users/swast/src/pandas/pandas/pandas/core/groupby/groupby.py", line 46, in <module>
    from pandas.core.index import (Index, MultiIndex,
  File "/Users/swast/src/pandas/pandas/pandas/core/index.py", line 2, in <module>
    from pandas.core.indexes.api import *
  File "/Users/swast/src/pandas/pandas/pandas/core/indexes/api.py", line 4, in <module>
    from pandas.core.indexes.base import (Index,
  File "/Users/swast/src/pandas/pandas/pandas/core/indexes/base.py", line 7, in <module>
    from pandas._libs import (lib, index as libindex, tslib as libts,
  File "pandas/_libs/index.pyx", line 27, in init pandas._libs.index
    from pandas._libs import algos, hashtable as _hash
  File "pandas/_libs/tslibs/period.pyx", line 59, in init pandas._libs.tslibs.period
  File "/Users/swast/src/pandas/pandas/pandas/tseries/offsets.py", line 2327, in <module>
    offset=BDay(), time_rule=None):
  File "/Users/swast/src/pandas/pandas/pandas/tseries/offsets.py", line 484, in __init__
    BaseOffset.__init__(self, n, normalize)
TypeError: object.__init__() takes no parameters
ERROR: could not load /Users/swast/src/pandas/pandas/pandas/conftest.py

$ pip freeze

alabaster==0.7.10
appnope==0.1.0
atomicwrites==1.1.5
attrs==17.4.0
Babel==2.5.3
backcall==0.1.0
cachetools==2.0.1
certifi==2018.4.16
chardet==3.0.4
colorlog==2.10.0
cycler==0.10.0
decorator==4.2.1
docutils==0.14
flake8==3.5.0
-e git+git@github.com:tswast/google-cloud-python.git@7f648ba34925f48a5e43cfc866413ce6cf1e0cc4#egg=google_api_core&subdirectory=api_core
google-auth==1.4.1
google-auth-oauthlib==0.2.0
google-cloud-bigquery==0.32.0
-e git+git@github.com:tswast/google-cloud-python.git@7f648ba34925f48a5e43cfc866413ce6cf1e0cc4#egg=google_cloud_core&subdirectory=core
google-resumable-media==0.3.1
googleapis-common-protos==1.5.3
idna==2.6
imagesize==1.0.0
ipython==6.3.1
ipython-genutils==0.2.0
jedi==0.11.1
Jinja2==2.10
kiwisolver==1.0.1
MarkupSafe==1.0
matplotlib==2.2.2
mccabe==0.6.1
mock==2.0.0
more-itertools==4.1.0
nox-automation==0.18.2
numpy==1.14.2
numpydoc==0.8.0
oauthlib==2.0.7
packaging==17.1
-e git+git@github.com:tswast/pandas.git@7829ad3290dc6894d24c1c853ffc4dabef50294a#egg=pandas
-e git+git@github.com:tswast/pandas-gbq.git@ade32a238d789a115788fe3e81e21aba34544a06#egg=pandas_gbq
parso==0.1.1
pbr==4.0.2
pexpect==4.4.0
pickleshare==0.7.4
pkginfo==1.4.2
pluggy==0.6.0
pockets==0.6.2
prompt-toolkit==1.0.15
protobuf==3.5.2.post1
ptyprocess==0.5.2
py==1.5.3
pyasn1==0.4.2
pyasn1-modules==0.2.1
pycodestyle==2.3.1
pyflakes==1.6.0
Pygments==2.2.0
pyparsing==2.2.0
pytest==3.6.2
python-dateutil==2.7.2
pytz==2018.4
requests==2.18.4
requests-oauthlib==0.8.0
requests-toolbelt==0.8.0
rsa==3.4.2
simplegeneric==0.8.1
six==1.11.0
snowballstemmer==1.2.1
Sphinx==1.7.4
sphinx-rtd-theme==0.3.0
sphinxcontrib-websupport==1.0.1
tqdm==4.23.4
traitlets==4.3.2
twine==1.11.0
urllib3==1.22
virtualenv==15.2.0
wcwidth==0.1.7

Problem description

I cannot run the tests due to this exception after updating to the latest commit. The stacktrace points to a line which was recently modified in #21341. I'll try rebasing on an older commit to see if that fixes it.

[WillAyd]

Did you rebuild your Cython extensions after pulling the master branch?

[tswast]

No, I missed that step. Is it python setup.py build_ext --inplace -j 4 as described at https://pandas.pydata.org/pandas-docs/stable/contributing.html#creating-a-python-environment-pip ?

[WillAyd]

That's correct. The error you are getting leads me to believe that's the case so I'm going to close this out, but feel free to reopen if that doesn't resolve it for you

[tswast]

That fixed it, thanks!