diff --git a/securedrop/create-dev-data.py b/securedrop/create-dev-data.py
index 2e4d753c63..4b8555213c 100755
--- a/securedrop/create-dev-data.py
+++ b/securedrop/create-dev-data.py
@@ -103,8 +103,8 @@ def create_source_and_submissions(num_submissions=2, num_replies=2):
     db.session.commit()
 
     print("Test source (codename: '{}', journalist designation '{}') "
-          "added with {} submissions and {} replies").format(
-              codename, journalist_designation, num_submissions, num_replies)
+          "added with {} submissions and {} replies".format(
+              codename, journalist_designation, num_submissions, num_replies))
 
 
 if __name__ == "__main__":  # pragma: no cover
diff --git a/securedrop/dockerfiles/xenial/python2/Dockerfile b/securedrop/dockerfiles/xenial/python2/Dockerfile
index f17d7bab21..07d252a6ef 100644
--- a/securedrop/dockerfiles/xenial/python2/Dockerfile
+++ b/securedrop/dockerfiles/xenial/python2/Dockerfile
@@ -9,9 +9,8 @@ ENV USER_ID ${USER_ID:-0}
 RUN apt-get update && \
     apt-get install -y paxctl && \
     { apt-get install -y libgtk2.0 || echo 'libgtk2.0 was not installed'; } && \
-    paxctl -cm /usr/bin/mono-sgen && dpkg-reconfigure mono-runtime-sgen
-
-RUN apt-get install -y devscripts vim \
+    paxctl -cm /usr/bin/mono-sgen && dpkg-reconfigure mono-runtime-sgen && \
+    apt-get install -y devscripts vim \
                        python-pip libpython2.7-dev libssl-dev secure-delete \
                        gnupg2 ruby redis-server firefox git xvfb haveged curl \
                        gettext paxctl x11vnc enchant libffi-dev sqlite3 gettext sudo
diff --git a/securedrop/dockerfiles/xenial/python3/Dockerfile b/securedrop/dockerfiles/xenial/python3/Dockerfile
index 72170c235c..051151ac5c 100644
--- a/securedrop/dockerfiles/xenial/python3/Dockerfile
+++ b/securedrop/dockerfiles/xenial/python3/Dockerfile
@@ -8,9 +8,8 @@ ENV USER_ID ${USER_ID:-0}
 # If running grsecurity kernel on the host, Memprotect must be disabled on mono-sgen in the container
 RUN apt-get update && apt-get install -y paxctl && \
     { apt-get install -y libgtk2.0 || echo 'libgtk2.0 was not installed'; } && \
-    paxctl -cm /usr/bin/mono-sgen && dpkg-reconfigure mono-runtime-sgen
-
-RUN apt-get install -y devscripts \
+    paxctl -cm /usr/bin/mono-sgen && dpkg-reconfigure mono-runtime-sgen && \
+    apt-get install -y devscripts \
                        python3-pip libpython3.5-dev libssl-dev secure-delete \
                        gnupg2 ruby redis-server firefox git xvfb haveged curl \
                        gettext paxctl x11vnc enchant libffi-dev sqlite3 gettext sudo \