Enforce pip to use python 2.7 for boto (#1093)

setup/management.sh

@@ -51,7 +51,7 @@ hide_output pip3 install --upgrade \
 # duplicity uses python 2 so we need to get the python 2 package of boto to have backups to S3.
 # boto from the Ubuntu package manager is too out-of-date -- it doesn't support the newer
 # S3 api used in some regions, which breaks backups to those regions.  See #627, #653.
-hide_output pip install --upgrade boto
+hide_output pip2 install --upgrade boto
 
 # CONFIGURATION