Print `ImportError` message during package testing

[jakirkham]

In the event a user wants to test the CuPy package on hardware, but gets an unexpected ImportError, it would be useful to share exactly why importing failed. Should give users a bit more information to aid in debugging the issue.

cc @mariusvniekerk @leofang

Checklist

• [x] Used a fork of the feedstock to propose changes
• [x] Bumped the build number (if the version is unchanged)
• [ ] Reset the build number to 0 (if the version changed)
• [x] Re-rendered with the latest conda-smithy (Use the phrase code>@<space/conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• [x] Ensured the license file is being packaged.

Fixes https://github.com/conda-forge/cupy-feedstock/issues/6

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[jakirkham]

@conda-forge-admin, please re-render.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-webservice.

I tried to re-render for you, but it looks like there was nothing to do.

[leofang]

Doesn't seem like we need this. Feel free to reopen if I am wrong.