osc linkpac with a wrong number of arguments results in scm sync error messages

[dcermak]

Describe the bug
Calling osc linkpac with the wrong number of arguments in a working copy results in an unrelated and unhelpful scmsync error message:

🏠/packages/obs/devel:BCI:SLCS:next 
🕙[ 11:52:45 ] ❯ osc linkpac devel:languages:python python-pip 
Directory '/home/dan/packages/obs/devel:BCI:SLCS:next' is not an OBS SCM working copy of a package

🏠/packages/obs/devel:BCI:SLCS:next took 2s 
🕙[ 11:53:20 ] ❯ osc linkpac
Directory '/home/dan/packages/obs/devel:BCI:SLCS:next' is not an OBS SCM working copy of a package

Versions

• Operating system: Fedora Linux 39 (Thirty Nine)
• Packages: osc-1.6.0-400.1.1.fc39.noarch

To Reproduce
Steps to reproduce the behavior:

1. cd path/to/a/checkout
2. osc linkpac

Expected behavior

An error that says "wrong number of arguments" would be nice.