1.0.3dev: Log exceptions from `changeset_modified` at warning level. Refs #11775.

For both `changeset_modified` and `changeset_added` print exceptions to the console when running the correspoding TracAdmin commands.


git-svn-id: http://trac.edgewall.org/intertrac/log:/branches/1.0-stable@13341 af82e41b-90c4-0310-8c96-b1721e28e2e2