Getting a SyntaxError on the last line of code in a Unison Merge script

Question

Hey brilliant minds out there,

I'm trying to get this Python script that I found working and can't figure out if it's just me or if the original poster didn't get the code right. This script is supposed to enable automatic conflict resolution in Unison by utilising the merge command in the prefs file by taking the two conflicting files and duplicating one of them with a datestamp in the filename. The original posing is here but there wasn't any indentation so I've had to go through and do it manually just by watching the errors that pop up. The error that I can't seem to get around now is

    File "/bin/unison_merge.py", line 5, in <module>
        PATH, CURRENT1, CURRENT2, NEW = sys.argv[1:]
ValueError: need more than 0 values to unpack

I'm hoping that someone out there will be able to help me out.

I've included the entire script below in the hope that it will help and that any other errors will be noticed :).

#!/usr/bin/env python2.7

import sys, os, datetime, os, filecmp

PATH, CURRENT1, CURRENT2, NEW = sys.argv[1:]

# see http://www.cis.upenn.edu/~bcpierce/unison/download/releases/stable/unison-manual.html#merge

promote_remote = False
backup_file_color = "red"

def is_suffix(a, b): return b[-len(a):] == a

def merge(PATH, CURRENT1, CURRENT2, NEW, promote_remote):
# CURRENT1 is copy of local, CURRENT2 is copy of remote

    if filecmp.cmp(CURRENT1, CURRENT2, shallow = False):
# special case -- files have same contents
# not a real conflict. just use local copy, no backup
        print "merge of identical files"
    os.link(CURRENT1, NEW)
    return

# PATH is relative to unison root.
# We need to know absolute path.
# We get it, assuming CURRENT1 is an absolute path
# referring to a file in the same subdirectory as PATH.

assert CURRENT1[0] == '/', "CURRENT1 (%s) is not absolute path" % CURRENT1

PATH_dir, PATH_tail = os.path.split(PATH)
ABS_dir = os.path.dirname(CURRENT1)

assert is_suffix(PATH_dir, ABS_dir), "%s not suffix of %s!" % (PATH_dir, ABS_dir)

ABS_PATH = os.path.join(ABS_dir, PATH_tail)

timestamp = datetime.datetime.now().strftime("%y%m%d_%H%M")
(root, ext) = os.path.splitext(PATH_tail)
for counter in range(100):
    counter = " %d" % counter if counter else ""
    filename = "%s @%s%s%s" % (root, timestamp, counter, ext)
    BACKUP = os.path.join(ABS_dir, filename)
    if not os.path.exists(BACKUP): break
else:
    assert False, "too many existing backups %s" % BACKUP

# promote_remote = False
# seems to retain file props, saving update in next sync?

    print "CONFLICT:", ABS_PATH

if promote_remote:
# resolve conflict by using remote copy, while backing up local to
    BACKUP
    CURRENT1, CURRENT2 = CURRENT2, CURRENT1
    print "CONFLICT remote saved as", filename
else:
    print "CONFLICT local saved as", filename

assert os.path.isfile(CURRENT1)
assert not os.path.exists(NEW)
assert not os.path.exists(BACKUP)

os.link(CURRENT1, BACKUP)
os.link(CURRENT2, NEW)

if backup_file_color and backup_file_color != 'none':
    mac_color_file(BACKUP, backup_file_color)

# note: coloring the tmp file NEW is useless - not propagated
# coloring the current file ABS_PATH causes UNISON to complain

# chmod -w BACKUP
# os.chmod(BACKUP, stat.S_IRUSR)

# just for coloring file in mac Finder
def mac_color_file(file, color):
    if not os.path.exists("/usr/bin/osascript"): return
color_map = {
"none":0,
"orange":1,
"red":2,
"yellow":3,
"blue":4,
"purple":5,
"green":6,
"gray":7,
}
assert color in color_map
assert file[0] == '/', 'absolute path required'
assert os.path.exists(file)
#see http://stackoverflow.com/questions/2435580/tagging-files-with-colors-in-os-x-finder-from-shell-scripts
#osascript -e "tell application \"Finder\" to set label index of alias POSIX
file ("$filename\" to $label")
cmd = '''/usr/bin/osascript -e 'tell application "Finder" to set label index of alias POSIX file "%s" to %d' > /dev/null ''' % (file, color_map[color])
try:
    retcode = subprocess.call(cmd, shell=True)
    if retcode < 0:
        print >>sys.stderr, "mac_color_file child was terminated by signal", retcode
    elif retcode > 0:
        print >>sys.stderr, "mac_color_file child returned", retcode
except OSError, e:
    print >>sys.stderr, "mac_color_file child failed:", e

### main ###

merge(PATH, CURRENT1, CURRENT2, NEW, promote_remote)

Answer 1

The try block doesn't have an accompanying except.

This tutorial page clarifies the use of the try..except structure: http://docs.python.org/tutorial/errors.html#handling-exceptions