ValueError: 'format' in __slots__ conflicts with class variable

Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-build-qe3ebgj7/progressbar/setup.py", line 5, in <module>
        import progressbar
      File "/tmp/pip-build-qe3ebgj7/progressbar/progressbar/__init__.py", line 59, in <module>
        from progressbar.widgets import *
      File "/tmp/pip-build-qe3ebgj7/progressbar/progressbar/widgets.py", line 121, in <module>
        class FileTransferSpeed(Widget):
      File "/public/home/zzh/.pyenv/versions/anaconda3-4.3.1/lib/python3.6/abc.py", line 133, in __new__
        cls = super().__new__(mcls, name, bases, namespace)
    ValueError: 'format' in __slots__ conflicts with class variable
    
    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-qe3ebgj7/progressbar/

今天在安裝ATCG的GDC Data Transfer Tool 軟件過程中，安裝幾個依賴的python包時出現以上錯誤。大致估計可能是python版本的問題。我pip安裝的是3.x的版本，這個包可能用的是2.x的版本。

用2.x的版本安裝后報錯問題解決

安裝完成后運行./gdc-client命令時，再次報錯

ImportError: /public/home/zzh/.pyenv/versions/2.7.13/lib/python2.7/site-packages/lxml-3.5.0b1-py2.7-linux-x86_64.egg/lxml/etree.so: undefined symbol: xmtent

谷歌了一下，可能是lxml依賴的一些 libraries 未安裝。