Yarn vendored packages impossible to patch

Hello,
we have packages provided to us through private repository, the package itself is not owned by us.
We add this with "file:" protocol of yarn:
```
{
"dependencies": {
"shim": "file:./vendor/shim-0.1.23.tgz"
}
}
```

When we try to patch this package with `yarn patch-package shim` it returns the following error:
error
`Package "" refers to a non-existing file '"/private/var/folders/kh/kgqx507n5b31w3676tsvkw3r0000gn/T/tmp-2705AUL26tJlAvfk/vendor/shim-0.1.23.tgz#73c29517ef20deb521e83f38b931a7d09fabdfbc"'`.

I've managed to overcome this issue manually, with:
1. put a breakpoint to line which corresponds to https://github.com/ds300/patch-package/blob/fbbeccd3025451d862b2b8786215e8fd111bec5a/src/makePatch.ts#L109
2. Run vscode in debug mode, so breakpoint would trigger
3. copy "vendor" folder to the `tmpRepoNpmRoot`
4. edit package.json file in `tmpRepoNpmRoot` to remove this fancy ending `#73c29517ef20deb521e83f38b931a7d09fabdfbc`
5. continue execution

So, for yarn managed projects we need to copy files itself along with package.json creation. Could this be implemented in patch-package itself?