pip install failed

trying to install poezio from Pypi :

(poezio-trunk)casper@falcon ~ % pip install poezio
Collecting poezio
Downloading poezio-0.9.tar.gz (1.0MB)
100% |████████████████████████████████| 1.0MB 944kB/s
Complete output from command python setup.py egg_info:
Traceback (most recent call last):
File "", line 1, in
File "/tmp/pip-build-A7j7DD/poezio/setup.py", line 64, in
with open('README.rst', encoding='utf-8') as readme_fd:
TypeError: 'encoding' is an invalid keyword argument for this function

---

Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-A7j7DD/poezio/