Server requires auth switch, but no auth switch handler provided

[DJ-DJL]

As per http://stackoverflow.com/questions/41941663/server-requires-auth-switch-but-no-auth-switch-handler-provided and mysqljs/mysql#1396

This error did not occur on our test mysql server, but it does occur on the production one.

When adding the authSwitchHandler as suggested the only thing that gets printed is { pluginName: '', pluginData: <Buffer > }
Doesn't seem very helpful.
debug: true added a whole load of stuff, some of which follows (redacted in case hex strings contains credentials:

Add command: Connection
Add command: Connection
 raw: <redacted>
2 undefined ==> Connection#handshakeInit(0,,60)
Server hello packet: capability flags:41516=(long flag, connect with db, compress, protocol 41, transactions, secure connection)
Sending handshake packet: flags:8582095=(long password, found rows, long flag, connect with db, odbc, local files, ignore space, protocol 41, ignore sigpipe, transactions, reserved, secure connection, multi results, session track)
2 59003828 <== Connection#handshakeInit(1,,79)
2 59003828 <== <redacted>
 raw: <redacted>
1 undefined ==> Connection#handshakeInit(0,,60)
Server hello packet: capability flags:41516=(long flag, connect with db, compress, protocol 41, transactions, secure connection)
Sending handshake packet: flags:8582095=(long password, found rows, long flag, connect with db, odbc, local files, ignore space, protocol 41, ignore sigpipe, transactions, reserved, secure connection, multi results, session track)
1 59003827 <== Connection#handshakeInit(1,,79)
1 59003827 <== <redacted>
Add command: Connection
 raw: fe
2 59003828 ==> Connection#handshakeResult(2,EOF,5)
Request ended
 raw: fe
1 59003827 ==> Connection#handshakeResult(2,EOF,5)
 raw: <redacted>
3 undefined ==> Connection#handshakeInit(0,,60)
Server hello packet: capability flags:41516=(long flag, connect with db, compress, protocol 41, transactions, secure connection)
Sending handshake packet: flags:8582095=(long password, found rows, long flag, connect with db, odbc, local files, ignore space, protocol 41, ignore sigpipe, transactions, reserved, secure connection, multi results, session track)
3 59003829 <== Connection#handshakeInit(1,,79)
3 59003829 <== <redacted>
 raw: fe
3 59003829 ==> Connection#handshakeResult(2,EOF,5)

[sidorares]

What's the server version you are using?

[DJ-DJL]

protocol_version	10
version	5.0.95-log
version_bdb	Sleepycat Software: Berkeley DB 4.1.24: (December 16, 2011)
version_comment	Source distribution
version_compile_machine	x86_64
version_compile_os	redhat-linux-gnu

[DJ-DJL]

I have tried connecting via a different method and get this message instead:
Authentication with old password no longer supported, use 4.1 style passwords.
I'm not sure if this relates to the same underlying problem or not?
I am already exploring avenues to address this alternative error.

[DJ-DJL]

Turns out this was indeed the problem.
Solution here: https://forums.mysql.com/read.php?38,593423,593423

Perhaps the error message could be improved?