Interpreter lookup fails when first `-p` value is absolute and missing

[barneygale]

We use virtualenv and tox to run tests against a commercial application that embeds its own Python interpreter. The location of that interpreter varies by OS, so we pass all the possible locations as -p values to virtualenv by providing multiple values of basepython on tox.ini.

Issue

When providing the -p / --python multiple time, virtualenv creation fails if a missing, absolute path occurs before an existing path.

Output of the virtual environment creation

# This works fine:
$ virtualenv -p this/doesnt/exist -p python3.9 dest
created virtual environment CPython3.9.5.final.0-64 in 363ms
[snip]
# But this fails
$ virtualenv -p /this/doesnt/exist -p python3.9 dest
FileNotFoundError: [Errno 2] No such file or directory: '/this/doesnt/exist'

I'd expect the absolute path to be handled just like the relative path, e.g. the failure should be ignored and we should move on to the next -p value.