bazel coverage produces empty coverage analysis reports and a message about missing GCov when running against a py_test target

# 🐞 bug report

### Affected Rule

The issue is caused by the rule: py_test()

### Is this a regression?

No

### Description

After the successful execution of the bazel test command I attempted to add the coverage tool too.
Unfortunately, I get output:

GCov does not exist at the given path: ''
Oct 13, 2025 12:50:34 PM com.google.devtools.coverageoutputgenerator.Main runWithArgs
WARNING: There was no coverage found.

I want to use the coverage (opensource) pip package for gathering coverage data of Python tests. I have no clue why running
**bazelisk coverage --combined_report=lcov //... --test_output=all** returns that GCov does not exist.

My test scripts are written with unittest framework, and they successfully run with bazelisk test :all --test_output=all

## 🔬 Minimal Reproduction

https://github.com/TeodorMalbasic/bazel_coverage_target_issue.git

## 🔥 Exception or Error

 

GCov does not exist at the given path: ''

Oct 13, 2025 12:50:34 PM com.google.devtools.coverageoutputgenerator.Main runWithArgs

WARNING: There was no coverage found.

## 🌍 Your Environment

**Operating System:**

  

Ubuntu 24.04

  

**Output of `bazel version`:**

  

bazel 8.4.2

  

**Rules_python version:**

  

Python 3.12.3 on machine, Python 3.12.11 in MODULE.bazel

  

**Anything else relevant?**

Start with the linked minimal reproduction and run `bazelisk coverage --combined_report=lcov //... --test_output=all`, then compare it with the successful `bazelisk test :all --test_output=all` run. Investigate how coverage is invoked for the `py_test()` target; done means the command produces a nonempty coverage analysis report without the missing-GCov warning.

Vom Indexierungsmodell aus dem Issue-Text verfasst.