Switch tests, docs, database settings from psycopg2 to psycopg (#6573)

* Fix isolation_level again, using the recommended method

* Use psycopg instead of psycopg2 in tests, docs

.github/workflows/qc_checks.yaml

@@ -309,7 +309,7 @@ jobs:
         uses: ./.github/actions/setup
         with:
           apt-dependency: gettext poppler-utils libpq-dev
-          pip-dependency: psycopg2 django-redis>=5.0.0
+          pip-dependency: psycopg django-redis>=5.0.0
           dev-install: true
           update: true
       - name: Run Tests
@@ -391,7 +391,7 @@ jobs:
         uses: ./.github/actions/setup
         with:
           apt-dependency: gettext poppler-utils libpq-dev
-          pip-dependency: psycopg2
+          pip-dependency: psycopg
           dev-install: true
           update: true
       - name: Run Tests

InvenTree/InvenTree/settings.py

@@ -571,10 +571,7 @@ db_options = db_config.get('OPTIONS', db_config.get('options', {}))
 
 # Specific options for postgres backend
 if 'postgres' in db_engine:  # pragma: no cover
-    from psycopg2.extensions import (
-        ISOLATION_LEVEL_READ_COMMITTED,
-        ISOLATION_LEVEL_SERIALIZABLE,
-    )
+    from django.db.backends.postgresql.psycopg_any import IsolationLevel
 
     # Connection timeout
     if 'connect_timeout' not in db_options:
@@ -640,9 +637,9 @@ if 'postgres' in db_engine:  # pragma: no cover
             'INVENTREE_DB_ISOLATION_SERIALIZABLE', 'database.serializable', False
         )
         db_options['isolation_level'] = (
-            ISOLATION_LEVEL_SERIALIZABLE
+            IsolationLevel.SERIALIZABLE
             if serializable
-            else ISOLATION_LEVEL_READ_COMMITTED
+            else IsolationLevel.READ_COMMITTED
         )
 
 # Specific options for MySql / MariaDB backend

docs/docs/start/install.md

@@ -159,7 +159,7 @@ grant all privileges on database inventree to myuser;
 The PostgreSQL python binding must also be installed (into your virtual environment):
 
 ```
-pip3 install psycopg2 pgcli
+pip3 install psycopg pgcli
 ```
 
 ### MySQL / MariaDB