Explicitly print exception from :try block

Reason: :try takes any output to the stderr as the exception, so traceback is 
never printed even though nothing is caught.
Balance error message text
Do not emit a warning about symlinks when it is not the problem
Do not remove one component from directory path
Normalize all paths before doing anything else
Move one if check into python code

Reason: this removes one useless indentation level that breaks “tabs for
indentation, spaces for alignment” rule.
Merge pull request #1025 from ZyX-I/fix-vim-troubleshooting

Fix some issues in Vim troubleshooting code