No trial shall be continued on account of the absence of any witness unless a subpoena
for the attendance of such witness has been served at least seven (7) days prior to the date
set for trial. This rule shall not dispense with the obligation to take the depositions of any
witness where the party or counsel requiring such attendance knows that such witness intends
to be absent from the district at the time of trial, or where such witness is not subject to
subpoena within this jurisdiction.