diff --git a/build/bot/ppa-build.sh b/build/bot/ppa-build.sh
index eab24e9ce..c28a3b5a2 100644
--- a/build/bot/ppa-build.sh
+++ b/build/bot/ppa-build.sh
@@ -2,10 +2,12 @@
 
 set -e -x
 
-# Note: this script is meant to be run in a Debian/Ubuntu docker container.
+# Note: this script is meant to be run in a Debian/Ubuntu docker container,
+# as user 'root'.
 
 # Install the required tools for creating source packages.
-apt-get install devscripts debhelper dput fakeroot python-bzrlib python-paramiko
+apt-get -yq --no-install-suggests --no-install-recommends install\
+     devscripts debhelper dput fakeroot
 
 # Add the SSH key of ppa.launchpad.net to known_hosts.
 echo '|1|7SiYPr9xl3uctzovOTj4gMwAC1M=|t6ReES75Bo/PxlOPJ6/GsGbTrM0= ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA0aKz5UTUndYgIGG7dQBV+HaeuEZJ2xPHo2DS2iSKvUL4xNMSAY4UguNW+pX56nAQmZKIZZ8MaEvSj6zMEDiq6HFfn5JcTlM80UwlnyKe8B8p7Nk06PPQLrnmQt5fh0HmEcZx+JU9TZsfCHPnX7MNz4ELfZE6cFsclClrKim3BHUIGq//t93DllB+h4O9LHjEUsQ1Sr63irDLSutkLJD6RXchjROXkNirlcNVHH/jwLWR5RcYilNX7S5bIkK8NlWPjsn/8Ua5O7I9/YoE97PpO6i73DTGLh5H9JN/SITwCKBkgSDWUt61uPK3Y11Gty7o2lWsBjhBUm2Y38CBsoGmBw==' >> ~/.ssh/known_hosts