Merge pull request #159 from jazzband/149-extra-psycopg2

#149 Added a clear message on ImportError when the psycopg2 package cannot be found.

CHANGES.rst

@@ -4,6 +4,13 @@ CHANGES
 4.2.0 (Unreleased)
 ------------------
 
+General:
+
+* #149 Added a clear message on ImportError when the psycopg2
+  package cannot be found.
+  Please refer to the following site for more information: 
+  https://django-redshift-backend.readthedocs.io/en/master/basic.html#installation
+
 Features:
 
 * #143 Add Django-5.0 support.

django_redshift_backend/base.py

@@ -15,11 +15,18 @@
 import django
 from django.utils import timezone
 from django.conf import settings
-from django.core.exceptions import FieldDoesNotExist
+from django.core.exceptions import FieldDoesNotExist, ImproperlyConfigured
 from django.db.models import Index
 from django.db.models.expressions import Col
 from django.db.utils import NotSupportedError, ProgrammingError
 
+try:
+    from psycopg2.extensions import Binary
+except ImportError:
+    raise ImproperlyConfigured(
+        "Error loading psycopg2 module. Please install as: `pip install django-redshift-backend[psycopg2]` or `pip install django-redshift-backend[psycopg2-binary]`. For more information, see https://django-redshift-backend.readthedocs.io/en/master/basic.html#installation"
+    )
+
 from ._vendor.django40.db.backends.base.introspection import FieldInfo, TableInfo
 from ._vendor.django40.db.backends.base.schema import (
     _is_relevant_relation,
@@ -37,8 +44,6 @@
     DatabaseIntrospection as BasePGDatabaseIntrospection,
 )
 from .meta import DistKey, SortKey
-from psycopg2.extensions import Binary
-
 from .psycopg2adapter import RedshiftBinary
 
 logger = logging.getLogger("django.db.backends")

tox.ini

@@ -28,13 +28,12 @@ DJANGO =
 
 [testenv]
 deps =
+    .[psycopg2-binary]
     coverage
-    psycopg2-binary>=2.7
     pytest
     pytest-cov
     mock>=2.0
     django-environ
-    py38: backports.zoneinfo
     dj32: Django>=3.2,<3.3
     dj40: Django>=4.0,<4.1
     dj42: Django>=4.2,<5.0