metadata update incomplete

[ptrebert]

The update_metadata.py script copies the CITATION.md and then prints the following messages and does nothing ...

LICENSE checking...
.editorconfig checking...
pyproject.toml checking...
files_updated? True
Update metadata files version in pyproject.toml? (y/n)y

[svenwillger]

The script also prints `"{file} updated!" even if the file couldn't be found on the server side and nothing happened.
Revise the script to add a check if desired file exists and/or actually was copied.

[svenwillger]

All stated metadata files are getting updated with a message if the update occurs. The pyproject.toml is downloaded if missing and if present the metadata files version is updated and the rest of the pyproject.toml stays untouched