Here's a log from my system that returns the Failed/Success message:

DUPLICITY: INFO 2 54999298190
DUPLICITY: . Processed volume 1145

DUPLICITY: DEBUG 1
DUPLICITY: . Registering (mktemp) temporary file /tmp/duplicity-T5XHyy-tempdir/mktemp-wg1ZQH-147

DUPLICITY: INFO 11
DUPLICITY: . AsyncScheduler: running task synchronously (asynchronicity disabled)

DUPLICITY: INFO 1
DUPLICITY: . Writing smb://tlittle@media/backups/duplicity-full.20120421T000419Z.vol1146.difftar.gz

DUPLICITY: WARNING 1
DUPLICITY: . Attempt 1 failed: Error: Connection timed out

DUPLICITY: DEBUG 1
DUPLICITY: . Backtrace of previous error: Traceback (innermost last):
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 309, in iterate
DUPLICITY: .     return fn(*args, **kwargs)
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 119, in copy_file
DUPLICITY: .     target.get_parse_name())
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 95, in handle_error
DUPLICITY: .     raise e
DUPLICITY: .  Error: Connection timed out
DUPLICITY: . 

DUPLICITY: INFO 1
DUPLICITY: . Writing smb://tlittle@media/backups/duplicity-full.20120421T000419Z.vol1146.difftar.gz

DUPLICITY: WARNING 1
DUPLICITY: . Attempt 2 failed: Error: Success

DUPLICITY: DEBUG 1
DUPLICITY: . Backtrace of previous error: Traceback (innermost last):
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 309, in iterate
DUPLICITY: .     return fn(*args, **kwargs)
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 119, in copy_file
DUPLICITY: .     target.get_parse_name())
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 95, in handle_error
DUPLICITY: .     raise e
DUPLICITY: .  Error: Success
DUPLICITY: . 

DUPLICITY: INFO 1
DUPLICITY: . Writing smb://tlittle@media/backups/duplicity-full.20120421T000419Z.vol1146.difftar.gz

DUPLICITY: WARNING 1
DUPLICITY: . Attempt 3 failed: Error: Success

DUPLICITY: DEBUG 1
DUPLICITY: . Backtrace of previous error: Traceback (innermost last):
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 309, in iterate
DUPLICITY: .     return fn(*args, **kwargs)
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 119, in copy_file
DUPLICITY: .     target.get_parse_name())
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 95, in handle_error
DUPLICITY: .     raise e
DUPLICITY: .  Error: Success
DUPLICITY: . 

DUPLICITY: INFO 1
DUPLICITY: . Writing smb://tlittle@media/backups/duplicity-full.20120421T000419Z.vol1146.difftar.gz

DUPLICITY: WARNING 1
DUPLICITY: . Attempt 4 failed: Error: Success

DUPLICITY: DEBUG 1
DUPLICITY: . Backtrace of previous error: Traceback (innermost last):
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 309, in iterate
DUPLICITY: .     return fn(*args, **kwargs)
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 119, in copy_file
DUPLICITY: .     target.get_parse_name())
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 95, in handle_error
DUPLICITY: .     raise e
DUPLICITY: .  Error: Success
DUPLICITY: . 

DUPLICITY: INFO 1
DUPLICITY: . Writing smb://tlittle@media/backups/duplicity-full.20120421T000419Z.vol1146.difftar.gz

DUPLICITY: ERROR 50 put '/tmp/duplicity-T5XHyy-tempdir/mktemp-wg1ZQH-147' 'smb://tlittle@media/backups/duplicity-full.20120421T000419Z.vol1146.difftar.gz'
DUPLICITY: . Success

DUPLICITY: DEBUG 1
DUPLICITY: . Removing still remembered temporary file /tmp/duplicity-T5XHyy-tempdir/mktemp-wg1ZQH-147

DUPLICITY: DEBUG 1
DUPLICITY: . Removing still remembered temporary file /tmp/duplicity-T5XHyy-tempdir/mkstemp-KK3ewN-1

** (deja-dup:15735): DEBUG: DuplicityInstance.vala:568: duplicity (15760) exited with value 50