构建docker镜像时，pip版本失败

Question

我正在尝试从我的python应用程序创建一个docker镜像，但是在尝试安装时我收到有关我的pip版本的错误消息：

Collecting tensorflow==1.2.1 (from -r requirements.txt (line 20))
Could not find a version that satisfies the requirement tensorflow==1.2.1 (from -r requirements.txt (line 20)) (from versions: )
No matching distribution found for tensorflow==1.2.1 (from -r requirements.txt (line 20))
You are using pip version 7.1.2, however version 9.0.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

但是当我查看我的pip版本时，它是最新的版本：

pip -V
pip 9.0.1 from /Users/xxx/anaconda/lib/python3.6/site-packages (python 3.6)

那么为什么docker链接到错误的pip版本呢？ 我在Mac High Sierra上运行。