[python] PY-84514 fix debugger import in isolated mode

there is already code to tweak `sys.path` to
workaround the isolated mode, we just need to
import all debugger stuff AFTER it


(cherry picked from commit acc72ae1a88e4533243a43c30bda4ab3b62c3ec9)

IJ-MR-179907

GitOrigin-RevId: af64cb82c3a79fbd133c303ddb0975f7b70a7f26

python/helpers/pydev/pydevd.py

@@ -8,14 +8,13 @@ import sys
 from contextlib import contextmanager
 import weakref
 
-from _pydevd_bundle.pydevd_daemon_thread import run_as_pydevd_daemon_thread
-
 # allow the debugger to work in isolated mode Python
 here = os.path.dirname(os.path.abspath(__file__))
 if here not in sys.path:
     sys.path.insert(0, here)
 
 from _pydevd_bundle.pydevd_collect_try_except_info import collect_return_info
+from _pydevd_bundle.pydevd_daemon_thread import run_as_pydevd_daemon_thread
 
 if sys.version_info[:2] < (2, 6):
     raise RuntimeError('The PyDev.Debugger requires Python 2.6 onwards to be run. If you need to use an older Python version, use an older version of the debugger.')

python/helpers/pydev/tests/test_pydevd.py

@@ -0,0 +1,19 @@
+import pytest
+
+from _pydevd_bundle.pydevd_constants import IS_PY3K
+
+if IS_PY3K:
+    import sys
+    import subprocess
+    from pathlib import Path
+
+
+@pytest.mark.python3(reason="`-I` is introduced in 3.4")
+def test_isolated_mode():
+    script = Path("pydevd.py")
+    result = subprocess.run(
+        [sys.executable, "-I", str(script), "--help"],
+        cwd=Path.cwd(),
+    )
+
+    assert result.returncode == 0