A lot of things updated.

Signed-off-by: Pavel Kirilin <win10@list.ru>

build.py

@@ -1,6 +1,7 @@
 import os
 from pathlib import Path
-from shutil import copytree, rmtree
+import shutil
+import subprocess
 
 
 CURRENT_DIR = Path(__file__).parent
@@ -29,15 +30,19 @@ def build(setup_kwargs):
     This script is useful for packaging the application.
     """
     print("Starting building frontend ...")
+    pnpm_path = shutil.which("pnpm")
+    if pnpm_path is None:
+        raise Exception("pnpm command is not available. PLease install pnpm.")
 
-    with DirChanger(CURRENT_DIR / "frontend"):
-        ret_status = os.system("pnpm build")
-        if ret_status != 0:
-            raise Exception("Frontend build failed.")
+    subprocess.run(
+        [pnpm_path, "build"],
+        cwd=CURRENT_DIR / "frontend",
+        check=True,
+    )
 
     print("Frontend build finished.")
-    rmtree(STATIC_OUTPUT_DIR, ignore_errors=True)
-    copytree(symlinks=True, src=DIST_DIR, dst=STATIC_OUTPUT_DIR)
+    shutil.rmtree(STATIC_OUTPUT_DIR, ignore_errors=True)
+    shutil.copytree(symlinks=True, src=DIST_DIR, dst=STATIC_OUTPUT_DIR)
 
     return setup_kwargs