Trouble reproducing errors for python/openpyxl

I have set up a local environment according to the instructions but I'm having trouble reproducing the bugs. For example:

```
python infra/helper.py reproduce openpyxl fuzz_formulae testcases/clusterfuzz-testcase-minimized-fuzz_formulae-5233715057393664
```
Returns
```
/out/fuzz_formulae.pkg: Running 1 inputs 100 time(s) each.
Running: /testcase
Executed /testcase in 353 ms
***
*** NOTE: fuzzing was not performed, you have only
*** executed the target code on a fixed set of inputs.
```

What does this mean? The testcase looks like a binary file so isn't much help. Maybe I've downloaded the wrong thing.

Based on testcase detail, I think I understand the problem. Not sure whether it really needs fixing as exceptions when reading files with junk is the default behaviour. But it could be done more gracefully.

Thanks for any pointers.

Start with the local setup instructions and the `infra/helper.py reproduce openpyxl fuzz_formulae` command shown in the report. Inspect the referenced `testcases/clusterfuzz-testcase-minimized-fuzz_formulae-5233715057393664` input and determine why the command only executes a fixed input; done means documenting the correct reproduction steps and clarifying the reported openpyxl behavior.

Written by the indexing model from the issue text.