[Bug] $$virtual karma unit tests

[acls]

• I'd be willing to implement a fix

Describe the bug

After upgrading to the latest yarn berry and updating my package dependencies my karma unit tests no longer run. The issue seems to be caused by #630 which changed virtual to $$virtual.

For some reason karma changes $$virtual to $virtual. Possibly some type of escaping bug/feature. This seems like a bug in karma, but it works using node_modules, so I would think yarn would want to correct it.

The packageLocation in the .pnp.js file is:
.yarn/$$virtual/karma-jasmine-virtual-d5e825a809/0/cache/karma-jasmine-npm-3.3.1-3b2922b99a-5eda66e5ce.zip/node_modules/karma-jasmine/

But karma ends up requesting:
.yarn/$virtual/karma-jasmine-virtual-d5e825a809/0/cache/karma-jasmine-npm-3.3.1-3b2922b99a-5eda66e5ce.zip/node_modules/karma-jasmine/lib/boot.js

To Reproduce

I created this repo that demonstrates the issue.

Environment if relevant (please complete the following information):

• OS: Linux
• Node version 10.21.0
• Yarn version 2.0.0-rc.36

Additional context

Previous version was 2.0.0-rc.6

[merceyz]

Upstream issue: karma-runner/karma#3530
Upstream fix: karma-runner/karma#3531

[acls]

That was quick. Thanks @merceyz!