Play Offline fails. Fails to load main class net.minecraft.client.main.Main

Please attach the crash report ([minecraft|http://hopper.minecraft.net/help/finding-minecraft-data-folder]/crash-reports/crash-<DATE>-client.txt), otherwise we can not diagnose this issue.
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Er, it's not a crash.
There's a one line error message, only, which I already pasted into the issue.

There is no crash report at that path, to paste. Unsurprisingly. 🙂

Here are the ERROR lines from the launcher log

ERROR Unexpected exception refreshing version list
UnknownHostexception
(call trace)
ERROR Exception whilst logging into profile
AuthenticationUnavailableException
(call trace)

All of this is totally expected in an offline state and all of these errors occur PRIOR to hitting Play Offline.

On running Play Offline, Game Output log says

JDK CMS deprecated warning that happens on every launch, including successful launch (1 line)

then

Error: Could not find or load main class net.minecraft.client.main.Main
(1 line)

In the Launcher log there are two more errors after

ERROR java.io.IOException: Stream closed
ERROR Game ended with bad state (exit code 1)

Note that I have 1.6.89-j not 1.6.91-j as I am affected by
MCL-9546
Legacy: Bootstrap is not updating launcher to 1.6.91-j

In case this is related

Apparently Linux users should upgrade to the latest Launcher version (eg 2.1.3676) which is available from the Mojang site).

Ok Play Offline works fine with the 2.1.3x launcher.

This can be moved to Legacy or closed.