diff --git a/doc/DEVELOPMENT.md b/doc/DEVELOPMENT.md
index 381c614..9dde2d3 100644
--- a/doc/DEVELOPMENT.md
+++ b/doc/DEVELOPMENT.md
@@ -61,7 +61,8 @@ Execute to generate Repo manifest
 
 ## Move database from prod to dev
 
-Copy the database image into `./image_db/prod_client.zip` and run `make db_restore_prod_client`. This will create a database
+Copy the database image into `./image_db/prod_client.zip` and run `make db_restore_prod_client`. This will create a
+database
 named `prod_client` ready to test.
 
 When moving database from prod to your dev environment, you want to remove email servers, backups and install user test
@@ -220,6 +221,24 @@ Update poetry, `./script/poetry/poetry_update.py`.
 
 Create docker, `make docker_build`.
 
+### Python version major change
+
+When you need to change python 3.7.17 to 3.8.10, do :
+
+```bash
+rm -r .venv
+make install_dev
+./.venv/bin/poetry lock --no-update
+```
+
+And update file script/install/install_locally.sh
+
+`ln -fs ${EL_HOME_ODOO}/odoo ${EL_HOME}/.venv/lib/python3.7/site-packages/`
+
+to
+
+`ln -fs ${EL_HOME_ODOO}/odoo ${EL_HOME}/.venv/lib/python3.8/site-packages/`
+
 # Pull request
 
 ## Show all pull requests from organization
diff --git a/doc/POETRY.md b/doc/POETRY.md
index 543a7f9..8c3adc6 100644
--- a/doc/POETRY.md
+++ b/doc/POETRY.md
@@ -34,3 +34,13 @@ Change version in file `./script/install/install_locally.sh` into constant `POET
 Erase directory `~/.poetry` and `./get-poetry.py`.
 
 Run installation script for OS, check `./script/install/install_locally.sh`.
+
+# FAQ
+
+## Got error "file could not be opened successfully"
+
+Delete cache at root of the project
+
+```bash
+rm -r cache
+```