issue 602041 shows a bunch of Shill crashes with output similar to issue 594336:

FATAL:chromeos_supplicant_process_proxy.cc(168)] Failed to get interface wlan0: fi.w1.wpa_supplicant1.InterfaceUnknown wpa_supplicant knows nothing about this interface.#012/usr/lib64/libbase-core-369476.so(base::debug::StackTrace::StackTrace()+0x14) [0x7fdb745a9a54]#012

issue 599599#c0 - c5 all show the same fatal crashes in Shill.

 issue 599318  lacks the shill crash stacks but has a similar error in 'messages' : 

Failed to get interface wlan0: fi.w1.wpa_supplicant1.InterfaceUnknown wpa_supplicant knows nothing about this interface.#012/usr/lib64/libbase-core-369476.so(base::debug::StackTrace::StackTrace()+0x14) [0x7fba563a8a54]#012

issue 593317 appears to all be the same Shill crash.

Root cause is  issue 604769 . Will keep this open for triaging purposes until that is resolved.

We decided not to fix the Shill crash whien wpa_supplicant fails.

We should try to improve the error message when this occurs.

Lowering priority and marking available.

+ejcaruso@, another Shill crash, FYI

+semenzato for shill reliability, maybe he's seen something like this recently?

No, I had not seen this, but I agree that if indeed this has the same cause as issue 594336, then crashing with an informative assertion failure is the right behavior.  I am not sure we crash very cleanly right now.

These tests failures seem to have mostly stopped: see issue 593317 and https://wmatrix.googleplex.com/retry_teststats/?days_back=120&tests=network_DefaultProfileServices.