pipenv install --pypi-mirror suppress by -i and --extra-index-url

[mlouielu]

Issue description

pipenv install --pypi-mirror suppress by -i and --extra-index-url

Expected result

Looking in indexes: https://foo, https://bar, https://pypi.python.org/simple

Actual result

➜  p pipenv install ppppp -i https://foo.com --extra-index-url https://bar.com --pypi-mirror https://pypi.python.org/simple 
Installing ppppp…
Looking in indexes: https://foo.com, https://bar.com
Collecting ppppp

Steps to replicate

Provide the steps to replicate (which usually at least includes the commands and the Pipfile).

$ pipenv install ppppp -i https://foo.com --extra-index-url https://bar.com --pypi-mirror https://pypi.python.org/simple 

[techalchemy]

Closing as a duplicate of #2494