Error: Ca

## Error

```
Ca
```

## Stack trace

```
/tracks/python/exercises/isogram:444
/tracks/python/exercises/isogram:191 in Ii
/tracks/python/exercises/isogram:192
```

## Tracking Details
- **Project**: exercism-js
- **Sentry**: [Error: Ca](https://thalamus-ai.sentry.io/issues/142435756/)
- **Culprit**: ?(tracks/python/exercises/isogram)
- **First seen:** Aug 23, 2026

Start with the linked Sentry event and inspect the reported stack trace for tracks/python/exercises/isogram, especially lines 444, 191, and 192. Trace the source of the "Ca" error and determine what behavior should be corrected; the issue is complete when the cause is identified and the same error no longer occurs.

Written by the indexing model from the issue text.