Problem solving for PIP upgrades

From:http://blog.chenxiaosheng.com/posts/2016-05-19/pip_upgrade_pip_failure.html

Today, when you install a Python package using the Python pip, you are always prompted:

# pip Install--upgrade pip
requirement already up-to-date:pip in/usr/local/lib/python2.7/dist-packages
are using PIP version 8.1.1, however version 8.1.2 is available.
You should consider upgrading via the ' pip install--upgrade pip ' command.

Try to follow the instructions to perform PIP install--upgrade pip, without any error, but the upgrade has been unsuccessful, baffled, when looking at the man Pip, find the following options:

-V,--verbose
    give more output. Option is additive, and can being used to the 3 times.

Try to execute pip install--upgrade PIP-VVV finally has more tips:

1 location (s) to search for versions of PIP:
* http://example.url/simple/pip/
getting page http://example.url/  simple/pip/
starting new HTTP Connection (1): Example.url
"get/simple/pip/http/1.1" 403 247 could not
fetch URL http://example.url/simple/pip/: 403 Client Error:forbidden for url:http://example.url/simple/pip/-skipping
I nstalled version (8.1.2) is most up-to-date (past Versions:none) requirement already UP-TO-DATE:PIP in/usr/local/li
B/python2.7/dist-packages/pip-8.1.2-py2.7.egg
Cleaning up ...

Only then found that in my ~/.pip/pip.conf configuration file, Index-url used an abandoned address, deleted files after the upgrade, everything back to normal.

Such an important debug information, the PIP defaults unexpectedly does not output, continues baffled. :-)