PIP install package SSLError

問題

使用pip安裝package：

$ pip install <package>

報錯：

WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, 'EOF occurred in violation of protocol (_ssl.c:1125)'))': xxx/yyy
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, 'EOF occurred in violation of protocol (_ssl.c:1125)'))': xxx/yyy
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, 'EOF occurred in violation of protocol (_ssl.c:1125)'))': xxx/yyy
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, 'EOF occurred in violation of protocol (_ssl.c:1125)'))': xxx/yyy
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, 'EOF occurred in violation of protocol (_ssl.c:1125)'))': xxx/yyy
Could not fetch URL https://pypi.org/xxx/yyy : There was a problem confirming the ssl certificate: … (Caused by SSLError(SSLEOFError(8, 'EOF occurred in violation of protocol (_ssl.c:1125)')))

原因

PIP版本太高。降低 pip 版本可以解決問題。
我的 pip 版本是21.0.1，報錯。降級為 20.2.3，問題解決。
（備注：我嘗試過折騰 SSL，然而沒用）

解決方法

我的python是在conda環境中的，可以按如下方法降級 pip：
$ conda install pip==20.2.3
需要確認是否降級:

The following packages will be DOWNGRADED:

  pip                                 21.0.1-py38h06a4308_0 --> 20.2.3-py38h06a4308_0

Proceed ([y]/n)? 

輸入 y 再回車即可。

如果是直接用系統環境中的python，可以這樣：
python -m pip install pip==20.2.3

降級完成后，再用pip install <package>就可以正常安裝了。

參考資料

https://v2as.com/article/9ac87b61-b9d2-4f2a-9198-87f183cf0ea1