various cleanups, better parallelism and build-dir structure

ci_scripts/remote_tests_python.sh

@@ -0,0 +1,41 @@
+#!/bin/bash 
+
+export BRANCH=${CIRCLE_BRANCH:?branch to build}
+export GITURL=${CIRCLE_REPOSITORY_URL:?git url of core-rust repo}
+
+export SSHTARGET=ci@b1.delta.chat
+
+# we construct the BUILDDIR such that we can easily share the
+# CARGO_TARGET_DIR between runs ("..")
+export BUILDDIR=ci_builds/$BRANCH/${CIRCLE_JOB:?jobname}/${CIRCLE_BUILD_NUM:?circle-build-number}
+
+set -e
+
+echo "--- Copying files to $SSHTARGET:$BUILDDIR"
+
+ssh -oStrictHostKeyChecking=no  $SSHTARGET mkdir -p "$BUILDDIR"
+git ls-tree -r $BRANCH -r --name-only >.rsynclist 
+rsync --files-from=.rsynclist -az ./ "$SSHTARGET:$BUILDDIR"
+# we seem to need .git for setuptools_scm versioning 
+rsync -az .git "$SSHTARGET:$BUILDDIR"
+
+echo "--- Running $CIRCLE_JOB remotely"
+
+ssh $SSHTARGET <<_HERE
+    set +x -e
+    cd $BUILDDIR
+    # let's share the target dir with our last run on this branch/job-type
+    # cargo will make sure to block/unblock us properly 
+    export CARGO_TARGET_DIR=\`pwd\`/../target
+    export TARGET=x86_64-unknown-linux-gnu
+    export RUSTC_WRAPPER=sccache
+    export DCC_PY_LIVECONFIG=$DCC_PY_LIVECONFIG
+
+    rm -rf virtualenv venv
+    virtualenv -q -p python3.7 venv 
+    source venv/bin/activate
+    set -x
+
+    pip install -q tox virtualenv
+    bash ci_scripts/run-python-test.sh 
+_HERE