ResolutionImpossible wrong message if package doesn't exist

[deeTEEcee]

Description

I have a requirements.txt file with moto==4.0.9 and constraints file with responses==0.23.0.
When I try to install with pip install -r <req> -c <constraints>, it leads to:

The conflict is caused by:
    moto 4.0.9 depends on responses>=0.13.0
    The user requested (constraint) responses==0.23.0
...
ERROR: ResolutionImpossible: for help visit https://pip.pypa.io/en/latest/topics/dependency-resolution/#dealing-with-dependency-conflicts

The reason for that being that the responses==0.23.0 doesn't exist. The latest is currently 0.22.0.

Expected behavior

I would expect pip to just tell me the package doesn't exist.

pip version

22.0.4 (Happens on latest version too)

Python version

3.7.12

OS

Macbook M1 Pro (Happens on Linux too)

Output

No response

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[cburroughs]

22.0.4 (Happens on latest version too)

To be explicit, this behavior still occurs on 23.2.1.