Set explicit python cache prefixes to avoid conflicts between versions.

The switch to use containers enables easily testing different python
versions from within the same source tree. This means Python builds with
differing ABI versions are compiling all our code. Avoid any potential
issues while moving between branches and versions by isolating the cache
directories for each environment of execution.

Author: albu-diku

envhelp/dpython

@@ -37,7 +37,7 @@ if [ -n "${PY}" ]; then
     DOCKER_FILE_SUFFIX="$PYTHON_SUFFIX"
 elif [ -n "${PYVER}" ]; then
     PY=3
-    PYTHON_SUFFIX="pyver-$PYVER"
+    PYTHON_SUFFIX="pyver_$PYVER"
     DOCKER_FILE_SUFFIX="pyver"
 else
     echo "No python version specified - please supply a PY env var"
@@ -61,6 +61,10 @@ PYTHONPATH='/usr/src/app'
 # default any variables for container development
 MIG_ENV=${MIG_ENV:-'docker'}
 
+# arrange for an explicit python cache hierarhy such that running different
+# containers with potentially radically different python APIs do not conflict
+PYTHONPYCACHEPREFIX="$PYTHONPATH/envhelp/output/__pycache.${PYTHON_SUFFIX}__"
+
 # determine if the image has changed
 echo -n "validating python $PY container.. "
 
@@ -84,5 +88,6 @@ echo "using image id $IMAGEID"
 ${DOCKER_BIN} run -it --rm \
     --mount "type=bind,source=$MIG_BASE,target=/usr/src/app" \
     --env "PYTHONPATH=$PYTHONPATH" \
+    --env "PYTHONPYCACHEPREFIX=$PYTHONPYCACHEPREFIX" \
     --env "MIG_ENV=$MIG_ENV" \
     "$IMAGEID" python$PY $@

envhelp/lpython

@@ -43,4 +43,8 @@ PYTHONPATH=${PYTHONPATH:-"$MIG_BASE"}
 # default any variables for local development
 MIG_ENV=${MIG_ENV:-'local'}
 
-PYTHONPATH="$PYTHONPATH" MIG_ENV="$MIG_ENV" "$PYTHON_BIN" "$@"
+# arrange for an explicit python cache hierarhy - this is primarily done for
+# consistency with the dpython script where it is necessary to avoid conflict
+PYTHONPYCACHEPREFIX="$PYTHONPATH/envhelp/output/__pycache.${MIG_ENV}__"
+
+PYTHONPATH="$PYTHONPATH" PYTHONPYCACHEPREFIX="$PYTHONPYCACHEPREFIX" MIG_ENV="$MIG_ENV" "$PYTHON_BIN" "$@"