Fix bug with EmailLogBackend.send_messages.
Fix bug with EmailLogBackend.send_messages.

The `logging.info` call was not properly using string interpolation.

dhcrzf/zulip,tommyip/zulip,timabbott/zulip,synicalsyntax/zulip,Galexrt/zulip,showell/zulip,kou/zulip,timabbott/zulip,zulip/zulip,Galexrt/zulip,timabbott/zulip,rishig/zulip,jackrzhang/zulip,shubhamdhama/zulip,rht/zulip,shubhamdhama/zulip,showell/zulip,punchagan/zulip,punchagan/zulip,synicalsyntax/zulip,showell/zulip,kou/zulip,brainwane/zulip,Galexrt/zulip,jackrzhang/zulip,rishig/zulip,mahim97/zulip,hackerkid/zulip,shubhamdhama/zulip,brainwane/zulip,tommyip/zulip,andersk/zulip,showell/zulip,brockwhittaker/zulip,kou/zulip,rht/zulip,brockwhittaker/zulip,rishig/zulip,rht/zulip,brainwane/zulip,andersk/zulip,showell/zulip,shubhamdhama/zulip,rht/zulip,dhcrzf/zulip,eeshangarg/zulip,timabbott/zulip,timabbott/zulip,zulip/zulip,tommyip/zulip,jackrzhang/zulip,andersk/zulip,Galexrt/zulip,kou/zulip,jackrzhang/zulip,kou/zulip,brainwane/zulip,Galexrt/zulip,mahim97/zulip,synicalsyntax/zulip,dhcrzf/zulip,eeshangarg/zulip,rishig/zulip,rishig/zulip,tommyip/zulip,shubhamdhama/zulip,punchagan/zulip,hackerkid/zulip,punchagan/zulip,hackerkid/zulip,mahim97/zulip,andersk/zulip,showell/zulip,mahim97/zulip,andersk/zulip,brockwhittaker/zulip,rishig/zulip,timabbott/zulip,synicalsyntax/zulip,mahim97/zulip,rht/zulip,tommyip/zulip,punchagan/zulip,jackrzhang/zulip,jackrzhang/zulip,hackerkid/zulip,eeshangarg/zulip,dhcrzf/zulip,zulip/zulip,brockwhittaker/zulip,tommyip/zulip,punchagan/zulip,hackerkid/zulip,synicalsyntax/zulip,tommyip/zulip,dhcrzf/zulip,kou/zulip,eeshangarg/zulip,eeshangarg/zulip,Galexrt/zulip,eeshangarg/zulip,jackrzhang/zulip,mahim97/zulip,zulip/zulip,kou/zulip,brockwhittaker/zulip,hackerkid/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,brockwhittaker/zulip,Galexrt/zulip,hackerkid/zulip,shubhamdhama/zulip,timabbott/zulip,brainwane/zulip,rishig/zulip,andersk/zulip,andersk/zulip,synicalsyntax/zulip,brainwane/zulip,brainwane/zulip,dhcrzf/zulip,punchagan/zulip,rht/zulip,dhcrzf/zulip,shubhamdhama/zulip,zulip/zulip,zulip/zulip,showell/zulip,synicalsyntax/zulip