MidiInAlsa::alsaMidiHandler: unknown MIDI input error!

[josephernest]

Thanks @superquadratic for this great module I have in at least two projects.

I use it only for MIDI input, with a callback.
I get randomly these errors, once every 4 or 5 notes usually:

MidiInAlsa::alsaMidiHandler: unknown MIDI input error!

when, and only when I open two different MIDI input devices at the same time (to provide MIDI input from 2 different MIDI devices at the same time)

midi1 = rtmidi.MidiIn()
midi1 = mycallback
midi1.open_port(port1)
midi2 = rtmidi.MidiIn()
midi2 = mycallback       # same callback 
midi2.open_port(port2)