infra: import CI speed (#14566)

Was taking 10 mins. Now a few seconds.

libs/core/Makefile

@@ -16,9 +16,7 @@ test_watch:
 	poetry run ptw --snapshot-update --now . -- -vv -x tests/unit_tests
 
 check_imports: $(shell find langchain_core -name '*.py')
-	for f in $^ ; do \
-		python -c "from importlib.machinery import SourceFileLoader; SourceFileLoader('x', '$$f').load_module()" || exit 1; \
-	done
+	poetry run python ./scripts/check_imports.py $^
 
 extended_tests:
 	poetry run pytest --only-extended $(TEST_FILE)

libs/core/scripts/check_imports.py

@@ -0,0 +1,17 @@
+import sys
+import traceback
+from importlib.machinery import SourceFileLoader
+
+if __name__ == "__main__":
+    files = sys.argv[1:]
+    has_failure = False
+    for file in files:
+        try:
+            SourceFileLoader("x", file).load_module()
+        except Exception:
+            has_faillure = True
+            print(file)
+            traceback.print_exc()
+            print()
+
+    sys.exit(1 if has_failure else 0)