Comment 6 for bug 1820055

I encountered this bug again:

```output
+ snapcraftctl prime
The interpreter 'python3' for 'bin/git-filter-repo' was resolved to '/usr/bin/python3'.
The command 'bin/git-filter-repo' has been changed to '/usr/bin/python3 $SNAP/bin/git-filter-repo' to safely account for the interpreter.
Failed to generate snap metadata: The specified command '/usr/bin/python3 $SNAP/bin/git-filter-repo' defined in the app 'git-filter-repo' does not match the pattern expected by snapd.
The command must consist only of alphanumeric characters, spaces, and the following special characters: / . _ # : $ -
ubuntu #
```

However, this time I failed to see any invalid characters in the `/usr/bin/python3 $SNAP/bin/git-filter-repo` which only contains alpha-numerics, space, dollar sign, and slashes.