I'm getting the following exception when trying to view a page in differential:

Command failed with error #1!
COMMAND
svn --non-interactive --no-auth-cache --username 'xxxxx' --password 'xxxxx' cat 'svn://fr-svn/lib2/tags/20150123/test/basic_init.py@27843'

STDOUT
(empty)

STDERR
svn: warning: W160013: File not found: revision 27843, path '/lib2/tags/20150123/test/basic_init.py'
svn: E200009: Could not cat all targets because some targets don't exist
svn: E200009: Illegal target for the requested operation

Details:

• The url for this revision is /rM27844
• It looks like differential is looking for the file with the wrong revision number (27843 instead of 27844)
• This commit was a tag, aka a copy from trunk to a new directory, but it was looks like it was invoked off the working copy (svn cp . ^/tags/20150123/). This makes the history a little wonky; it shows up as a copy of the base directory (trunk->20150123) as well as some of the individual files from the same base revision.

Let me know if there's more info that would be helpful.