rpm-py-installer: Download binaries

Instead of building from source.

Signed-off-by: Zack Cerza <zack@redhat.com>

devtools/containers/centos/Dockerfile

@@ -19,6 +19,7 @@ RUN \
     python-pip \
     python-psycopg2 \
     python-qpid-proton \
-    python-requests-kerberos && \
+    python-requests-kerberos \
+    yumdownloader && \
   pip install -U 'pip==9.0.1' && \
   pip install -U tox

devtools/containers/fedora/Dockerfile

@@ -1,6 +1,7 @@
 FROM fedora:32
 RUN \
   dnf install -y \
+  'dnf-command(download)' \
   gcc \
   git \
   glib2-devel \