Trying to get direct piping of log analytics to work on an Apache 2.4.7 / Ubuntu 14.04 system.
From looking at issues #3757, #3163 and #6200 something like this in the Apache conf file should work:

CustomLog "|/usr/bin/python -u /var/www/piwik/misc/log-analytics/import_logs.py --url=http://testsrv/piwik/ - --idsite=1 --log-format-name=common_vhost" vhost_combined

But this doesn't add any data to Piwik (checked in PMA, and accordingly nothing in the web UI). Adding --output=/var/log/piwik/test.log or checking Apache's error.log doesn't provide more clues (I can provoke errors in both files by using incorrect syntax or unknown option names).

The access log is in the vhost_combined format and the following as root does work:

tail -n1 access.log | /usr/bin/python -u /var/www/piwik/misc/log-analytics/import_logs.py --url=http://testsrv/piwik/ - --idsite=1 --log-format-name=common_vhost

It correctly adds the last page hit ("1 requests imported to 1 sites"), but when omitting the last option (--log-format-name=common_vhost) it gives:

0 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
Parsing log (stdin)...
0 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
0 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
0 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
0 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
0 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
0 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
0 lines parsed, 0 lines recorded, 0 records/sec (avg), 0 records/sec (current)
Fatal error: cannot automatically determine the log format using the first 100000 lines of the log file. 
Maybe try specifying the format with the --log-format-name command line argument.

I've tried various permutations, verbosely copying from misc/log-analytics/README.md and the threads linked above (especially since #3757 concludes that something somehow does work), but can't get a clear handle on what is going wrong. It looks as if it should be working, so any hints or an up to date how-to are appreciated.