Fix failing pip on CI (#224)

Specify a cache directory for each parallel pip run

Author: pylessard

scripts/activate-venv.sh

@@ -15,6 +15,17 @@ log() { echo -e "\x1B[92m[OK]\x1B[39m $@"; }
 
 source "$VENV_ROOT/bin/activate"
 
+MODULE_FEATURE="[dev]"
+if ! [[ -z "${BUILD_CONTEXT+x}" ]]; then
+    if [[ "$BUILD_CONTEXT" == "ci" ]]; then
+        MODULE_FEATURE="[test]" # Will cause testing tools to be installed.
+        export PIP_CACHE_DIR=$VENV_ROOT/pip_cache   # Avoid concurrent cache access issue on CI
+        echo "PIP_CACHE_DIR=${PIP_CACHE_DIR}"
+    fi
+fi
+
+pip3 cache info
+
 if ! pip3 show wheel 2>&1 >/dev/null; then
     log "Installing wheel..."
     pip3 install wheel
@@ -24,13 +35,6 @@ if ! pip3 show wheel 2>&1 >/dev/null; then
     pip3 install --upgrade setuptools
 fi
 
-MODULE_FEATURE="[dev]"
-if ! [[ -z "${BUILD_CONTEXT+x}" ]]; then
-    if [[ "$BUILD_CONTEXT" == "ci" ]]; then
-        MODULE_FEATURE="[test]" # Will cause testing tools to be installed.
-    fi
-fi
-
 if ! diff "$PY_MODULE_ROOT/setup.py" "$VENV_ROOT/cache/setup.py" 2>&1 >/dev/null; then
     log "Install inside venv"
     pip3 install -e "${PY_MODULE_ROOT}${MODULE_FEATURE}"