Hi @talklittle - Apologies for the late reply myself. I was hoping to have additional news but a fix has taken on a larger scope.
Our team is actively discussing the appropriate next steps for updating volley which involves support for Android M in addition to this fix.
Since you are using the open source version, one “right now” option is making a quick fork of https://github.com/mopub/mopub-volley and merging in the necessary changes from the https://github.com/mcxiaoke/android-volley library to resolve your crash.
We’ll follow up when this issue has been resolved officially by MoPub.
Also for future support needs, in addition to posting here, I recommend sending an email to support@mopub.com. That email feeds directly into the MoPub specific ticket queue and will provide an additional level of visibility to any issues you are experiencing.