Trap illegal encoding exception thrown by tcl9 when a file contains invalid UTF-8 and skip the package with a warningUnmaintained packages may contain illegal characters and we do not want the UI to crash in this situation
Limit files__tcl_file_common_errors test to installed packagesUnmaintained packages may ship files with invalid encodings, which tcl9 won't tolerate anymore.
Improve test - skip packages that are not installed before we check the info file - ensure all installed packages have an info fileThis fixes the test for tcl9, where some unmaintained packages may fail the file parsing because of invalid encoding.