MacOS Sierra no longer auto-loads SSH keys stored in Keychain. To correct this, add this plist to `~/Library/LaunchAgents`. To load it immediately, run `launchctl load ~/Library/LaunchAgents/SshAddA.plist`.

SshAddA.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>Label</key>
  <string>ssh-add-a</string>
  <key>ProgramArguments</key>
  <array>
    <string>ssh-add</string>
    <string>-A</string>
  </array>
  <key>RunAtLoad</key>
  <true/>
</dict>
</plist>