Fix _NamespacePath concatenation error in file_path function

Convert odoo.addons.__path__ to list before concatenation with [root_path]
to fix TypeError when using Python 3.7+ namespace packages.

Error: unsupported operand type(s) for +: '_NamespacePath' and 'list'
Location: odoo/tools/misc.py:169

Added documentation explaining the fix in docs/PATCH_ADDONS_PATH.md

🤖 assisted by claude

docs/PATCH_ADDONS_PATH.md

@@ -0,0 +1,48 @@
+# Fix for _NamespacePath Concatenation Error
+
+## Issue
+
+After upgrading, Odoo failed to start with the following error:
+
+```
+TypeError: unsupported operand type(s) for +: '_NamespacePath' and 'list'
+```
+
+This occurred in `odoo/tools/misc.py:169` in the `file_path()` function.
+
+## Root Cause
+
+In Python 3.7+, namespace packages use `_NamespacePath` objects for the `__path__` attribute. This special type cannot be directly concatenated with a Python list using the `+` operator.
+
+The problematic code was:
+```python
+addons_paths = odoo.addons.__path__ + [root_path]
+```
+
+When `odoo.addons.__path__` is a `_NamespacePath` object, attempting to add it to a list `[root_path]` raises a `TypeError`.
+
+## Solution
+
+Convert the `_NamespacePath` to a list before concatenation:
+
+```python
+addons_paths = list(odoo.addons.__path__) + [root_path]
+```
+
+## File Modified
+
+- `odoo-bringout-oca-ocb-base/odoo/tools/misc.py` line 169
+
+## Related Code
+
+The `file_path()` function is used throughout Odoo to:
+- Verify file paths under known `addons_path` directories
+- Locate module resources (icons, static files, etc.)
+- Validate file access for security purposes
+
+This fix ensures the function can properly construct the list of addon paths to search.
+
+## References
+
+- Python namespace packages: [PEP 420](https://www.python.org/dev/peps/pep-0420/)
+- Working commit reference: 3f19943cec2680164696765266fc0cdb4e9220c5