pbr 5.2.1需使用中科大的源，豆瓣的不行

-bash-4.2$ .tox/tempest/bin/pip install pbr==5.2.1
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7.
Looking in indexes: https://pypi.douban.com/simple/
Collecting pbr==5.2.1
  ERROR: Could not find a version that satisfies the requirement pbr==5.2.1 (from versions: 0.5.2.5.g5b3e942, 0.5.0, 0.5.1, 0.5.2, 0.5.4, 0.5.5, 0.5.6, 0.5.7, 0.5.8, 0.5.10, 0.5.11, 0.5.12, 0.5.13, 0.5.14, 0.5.15, 0.5.16, 0.5.17, 0.5.18, 0.5.19, 0.5.20, 0.5.21, 0.5.22, 0.5.23, 0.6, 0.7.0, 0.8.0, 0.8.1, 0.8.2, 0.9.0, 0.10.0, 0.10.1, 0.10.2, 0.10.3, 0.10.4, 0.10.5, 0.10.6, 0.10.7, 0.10.8, 0.11.0, 0.11.1, 1.0.0, 1.0.1, 1.1.0, 1.1.1, 1.2.0, 1.3.0, 1.4.0, 1.5.0, 1.6.0, 1.7.0, 1.8.0, 1.8.1, 1.9.0, 1.9.1, 1.10.0, 2.0.0, 2.1.0, 3.0.0, 3.0.1, 3.1.0, 3.1.1, 4.0.0, 4.0.1, 4.0.2, 4.0.3, 4.0.4, 4.1.0, 4.1.1, 4.2.0, 4.3.0, 5.0.0, 5.1.0, 5.1.1, 5.1.2, 5.1.3, 5.2.0)
ERROR: No matching distribution found for pbr==5.2.1

-bash-4.2$ .tox/tempest/bin/pip install pbr==5.2.1 -i https://pypi.mirrors.ustc.edu.cn/simple/
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7.
Looking in indexes: https://pypi.mirrors.ustc.edu.cn/simple/
Collecting pbr==5.2.1
  WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ReadTimeoutError("HTTPSConnectionPool(host='pypi.mirrors.ustc.edu.cn', port=443): Read timed out. (read timeout=15)",)': /simple/pbr/
  Downloading https://mirrors.tuna.tsinghua.edu.cn/pypi/web/packages/49/a2/e641de6c7e559e0a03a8d3c7b42199158b17a8cf2f96e11e7f725c2e730d/pbr-5.2.1-py2.py3-none-any.whl (108kB)
     |████████████████████████████████| 112kB 1.6MB/s
Installing collected packages: pbr
Successfully installed pbr-5.2.1