Fix GPT-SoVITS module search path

app.py

@@ -161,9 +161,12 @@ def dataset_prepared():
 
 def build_process_env():
     env = os.environ.copy()
+    python_path_parts = [str(GPT_SOVITS_DIR), str(GPT_SOVITS_DIR / "GPT_SoVITS")]
+    if env.get("PYTHONPATH"):
+        python_path_parts.append(env["PYTHONPATH"])
     env.update(
         {
-            "PYTHONPATH": str(GPT_SOVITS_DIR),
+            "PYTHONPATH": os.pathsep.join(python_path_parts),
             "inp_text": str(INPUT_LIST),
             "inp_wav_dir": str(AUDIO_DIR),
             "exp_name": EXP_NAME,