cubicweb-email #2836573 mailbox.UnixMailbox is deprecated in py 2.6 [validation pending]

prioritynormal
typebug
done in1.10.0
load0.200
load left0.000
closed by#2c8bceb8e9bf [mboximport] UnixMailbox is deprecated in python 2.6. Closes #2836573
patch[mboximport] UnixMailbox is deprecated in python 2.6. Closes #2836573 [applied]