pip 跳过升级，不满足时表示要求已经满足

Question

这是 pip install --upgrade 的输出：

[vagrant@cclab8-ht-esx-11 f5]$ sudo pip install f5-icontrol-rest --upgrade
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.org/simple, https://apds-web1.noc.bluecoatcloud.com/symc_pypi/symc_pypi_server.wsgi
Collecting f5-icontrol-rest
  Using cached https://files.pythonhosted.org/packages/e0/44/91979de0a81253d025a0814f16f53df46d3ed3edd5b9fd7181f28a9dd0bb/f5-icontrol-rest-1.3.13.tar.gz
Requirement already satisfied, skipping upgrade: requests<3,>=2.5.0 in /usr/lib/python2.7/site-packages (from f5-icontrol-rest) (2.21.0)
Requirement already satisfied, skipping upgrade: urllib3<1.25,>=1.21.1 in /usr/lib/python2.7/site-packages (from requests<3,>=2.5.0->f5-icontrol-rest) (1.24.1)
Requirement already satisfied, skipping upgrade: chardet<3.1.0,>=3.0.2 in /usr/lib/python2.7/site-packages (from requests<3,>=2.5.0->f5-icontrol-rest) (3.0.4)
Requirement already satisfied, skipping upgrade: idna<2.9,>=2.5 in /usr/lib/python2.7/site-packages (from requests<3,>=2.5.0->f5-icontrol-rest) (2.8)
Requirement already satisfied, skipping upgrade: certifi>=2017.4.17 in /usr/lib/python2.7/site-packages (from requests<3,>=2.5.0->f5-icontrol-rest) (2018.11.29)
Building wheels for collected packages: f5-icontrol-rest
  Building wheel for f5-icontrol-rest (setup.py) ... done
  Stored in directory: /root/.cache/pip/wheels/12/43/4c/9c3051759105429cd633ed53ece367db44b082fce01c28db46
Successfully built f5-icontrol-rest
Installing collected packages: f5-icontrol-rest
  Found existing installation: f5-icontrol-rest 1.3.12
    Uninstalling f5-icontrol-rest-1.3.12:
      Successfully uninstalled f5-icontrol-rest-1.3.12
Successfully installed f5-icontrol-rest-1.3.13
You are using pip version 19.0.2, however version 19.1.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

问题是我的系统请求包是2.21.0版本，2.21.0不大于等于2.5.0，pip却说满足要求。

我不明白这一行：

Requirement already satisfied, skipping upgrade: requests<3,>=2.5.0 in /usr/lib/python2.7/site-packages (from f5-icontrol-rest) (2.21.0)

有人明白为什么满足要求吗？为什么请求没有升级？

Answer 1

是的，2.5.0 与 2.50.0 不同。