Analyse following RPM build log snippet. Describe contents accurately, without speculation or suggestions for resolution.            
Your analysis must be as concise as possible, while keeping relevant information intact.
Snippet: 
:: [ 20:23:27 ] :: [  BEGIN   ] :: Get a screenshot :: actually running 'tmux capture-pane -J -p -t bz1814526'
server exited unexpectedly
:: [ 20:23:27 ] :: [   FAIL   ] :: Get a screenshot (Expected 0, got 1)

Reports failure of tmux tool