ci: install all Python dependecies via script

Some Python 2 modules no longer exist in Debian bullseye, so trying to
satisfy all build-dependencies in d/control would fail there.  For now
just install them in `run-ci` where we can modify the list of package
to install dynamically.

debian/control

@@ -16,20 +16,6 @@ Build-Depends: alembic,
                lintian,
                postgresql-12 | postgresql-11 | postgresql-9.6 | postgresql-9.4,
                postgresql-12-debversion | postgresql-11-debversion | postgresql-9.6-debversion | postgresql-9.4-debversion,
-               python-all-dev,
-               python-apt,
-               python-coverage,
-               python-debian,
-               python-debianbts,
-               python-ldap,
-               python-psycopg2,
-               python-pytest,
-               python-pytest-cov,
-               python-rrdtool,
-               python-six,
-               python-sqlalchemy,
-               python-tabulate,
-               python-yaml,
                python3-apt,
                python3-debian,
                python3-psycopg2,

debian/run-ci

@@ -117,24 +117,29 @@ run_apt-get update
 run_apt-get install -y build-essential
 run_apt-get build-dep -y .
 
+python_deps=(
+    python3-all-dev
+    python3-apt
+    python3-coverage
+    python3-debian
+    python3-debianbts
+    python3-ldap
+    python3-psycopg2
+    python3-pytest
+    python3-pytest-cov
+    python3-rrdtool
+    python3-six
+    python3-sqlalchemy
+    python3-tabulate
+    python3-yaml
+)
+
 if [ "x$DAK_PYTHON3" != "x" ]; then
     run_apt-get install -y --no-install-recommends \
-        2to3 \
-        python3-coverage \
-        python3-debian \
-        python3-debianbts \
-        python3-ldap \
-        python3-psycopg2 \
-        python3-pytest \
-        python3-pytest-cov \
-        python3-rrdtool \
-        python3-six \
-        python3-sqlalchemy \
-        python3-tabulate \
-        python3-yaml \
-        python3-apt \
-
-
+        2to3 ${python_deps[@]}
+else
+    run_apt-get install -y --no-install-recommends \
+        ${python_deps[@]/#python3-/python-}
 fi
 
 section_end install_dep