Fixed wording to be more explicit

One has to assume the original file uploaded (the very first time) is
the right and canonical version. If files change somehow it's most
likely to be a disk corruption issue

tablesnap

@@ -124,8 +124,10 @@ class UploadHandler(pyinotify.ProcessEvent):
 
         if key.size != stat.st_size:
             log.warning('ATTENTION: your source (%s) and target (%s) sizes '
-                'differ, you should take a look. Will skip this file to '
-                'avoid future complications' % (filename, keyname, ))
+                'differ, you should take a look. As immutable files '
+                'never change, one must assume the local file got corrupted '
+                'and the right version is the one in S3. Will skip this file '
+                'to avoid future complications' % (filename, keyname, ))
             return True
         else:
             # Compute MD5 sum of file
@@ -159,7 +161,9 @@ class UploadHandler(pyinotify.ProcessEvent):
             log.info("Keyname %s already exists, skipping upload" % keyname)
         else:
             log.warning('ATTENTION: your source (%s) and target (%s) MD5 '
-                'hashes differ, you should take a look. Will skip this file '
+                'hashes differ, you should take a look. As immutable files '
+                'never change, one must assume the local file got corrupted '
+                'and the right version is the one in S3. Will skip this file '
                 'to avoid future complications' % (filename, keyname, ))
             return True