[tor-relays] Tor bridge and obfs4proxy

[Arisbe]

I need someone's bridge experience.  I had an HD crash and lost one of 
my Tor bridges.  So, I'm rebuilding on a leased VPS.  First I tried with 
Debian 8 and then with ubuntu 16.04 when Debian didn't work.  With both 
operating systems I get a warning message when I start Tor.  Tor is the 
latest version as is obfs4proxy:

Sep 04 13:39:41.641 [warn] Strange ServerTransportPlugin type 'obfs4'
Sep 04 13:39:41.641 [warn] Failed to parse/validate config: Invalid 
server transport line. See logs for details.

There are no log entries.  Apparently Tor starts without the proxy.  I 
have configured torrc as follows:

ServerTransportPlugin obfs3 obfs4 exec /usr/bin/obfs4proxy

ExtORPort auto

/usr/bin/ does contain the obfs4proxy file.

Does anyone know my problem?  Is there a 'tell-all' explanation of 
obfs4proxy?

Thanks, Arisbe