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/

今天在安装ATCG的GDC Data Transfer Tool 软件过程中，安装几个依赖的python包时出现以上错误。大致估计可能是python版本的问题。我pip安装的是3.x的版本，这个包可能用的是2.x的版本。

用2.x的版本安装后报错问题解决

安装完成后运行./gdc-client命令时，再次报错

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依赖的一些 libraries 未安装。