diff --git a/django/db/backends/dummy/base.py b/django/db/backends/dummy/base.py
index 602bfb8fe6..126083cd50 100644
--- a/django/db/backends/dummy/base.py
+++ b/django/db/backends/dummy/base.py
@@ -26,14 +26,6 @@ def ignore(*args, **kwargs):
     pass
 
 
-class DatabaseError(Exception):
-    pass
-
-
-class IntegrityError(DatabaseError):
-    pass
-
-
 class DatabaseOperations(BaseDatabaseOperations):
     quote_name = complain
 
diff --git a/django/db/backends/mysql/base.py b/django/db/backends/mysql/base.py
index 472b2b98df..cce3b9de99 100644
--- a/django/db/backends/mysql/base.py
+++ b/django/db/backends/mysql/base.py
@@ -52,10 +52,6 @@ if (version < (1, 2, 1) or (
     raise ImproperlyConfigured("MySQLdb-1.2.1p2 or newer is required; you have %s" % Database.__version__)
 
 
-DatabaseError = Database.DatabaseError
-IntegrityError = Database.IntegrityError
-
-
 def adapt_datetime_warn_on_aware_datetime(value, conv):
     # Remove this function and rely on the default adapter in Django 2.0.
     if settings.USE_TZ and timezone.is_aware(value):
diff --git a/django/db/backends/oracle/base.py b/django/db/backends/oracle/base.py
index 9fafd43b34..55b75c3ef4 100644
--- a/django/db/backends/oracle/base.py
+++ b/django/db/backends/oracle/base.py
@@ -63,9 +63,6 @@ from .operations import DatabaseOperations                  # NOQA isort:skip
 from .schema import DatabaseSchemaEditor                    # NOQA isort:skip
 from .utils import Oracle_datetime, convert_unicode         # NOQA isort:skip
 
-DatabaseError = Database.DatabaseError
-IntegrityError = Database.IntegrityError
-
 
 class _UninitializedOperatorsDescriptor(object):
 
@@ -241,7 +238,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
                 cursor.execute("SELECT 1 FROM DUAL WHERE DUMMY %s"
                                % self._standard_operators['contains'],
                                ['X'])
-            except DatabaseError:
+            except Database.DatabaseError:
                 self.operators = self._likec_operators
                 self.pattern_ops = self._likec_pattern_ops
             else:
@@ -479,7 +476,7 @@ class FormatStylePlaceholderCursor(object):
             return self.cursor.execute(query, self._param_generator(params))
         except Database.DatabaseError as e:
             # cx_Oracle <= 4.4.0 wrongly raises a DatabaseError for ORA-01400.
-            if hasattr(e.args[0], 'code') and e.args[0].code == 1400 and not isinstance(e, IntegrityError):
+            if hasattr(e.args[0], 'code') and e.args[0].code == 1400 and not isinstance(e, Database.IntegrityError):
                 six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
             raise
 
@@ -498,7 +495,7 @@ class FormatStylePlaceholderCursor(object):
             return self.cursor.executemany(query, [self._param_generator(p) for p in formatted])
         except Database.DatabaseError as e:
             # cx_Oracle <= 4.4.0 wrongly raises a DatabaseError for ORA-01400.
-            if hasattr(e.args[0], 'code') and e.args[0].code == 1400 and not isinstance(e, IntegrityError):
+            if hasattr(e.args[0], 'code') and e.args[0].code == 1400 and not isinstance(e, Database.IntegrityError):
                 six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
             raise
 
diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
index 1ab05d81f6..d188f37853 100644
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -44,9 +44,6 @@ from .schema import DatabaseSchemaEditor                    # NOQA isort:skip
 from .utils import utc_tzinfo_factory                       # NOQA isort:skip
 from .version import get_version                            # NOQA isort:skip
 
-DatabaseError = Database.DatabaseError
-IntegrityError = Database.IntegrityError
-
 if six.PY2:
     psycopg2.extensions.register_type(psycopg2.extensions.UNICODE)
     psycopg2.extensions.register_type(psycopg2.extensions.UNICODEARRAY)
@@ -239,7 +236,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         nodb_connection = super(DatabaseWrapper, self)._nodb_connection
         try:
             nodb_connection.ensure_connection()
-        except (DatabaseError, WrappedDatabaseError):
+        except (Database.DatabaseError, WrappedDatabaseError):
             warnings.warn(
                 "Normally Django will use a connection to the 'postgres' database "
                 "to avoid running initialization queries against the production "
diff --git a/django/db/backends/sqlite3/base.py b/django/db/backends/sqlite3/base.py
index e8b707861f..ff78adaffa 100644
--- a/django/db/backends/sqlite3/base.py
+++ b/django/db/backends/sqlite3/base.py
@@ -45,9 +45,6 @@ from .introspection import DatabaseIntrospection            # isort:skip
 from .operations import DatabaseOperations                  # isort:skip
 from .schema import DatabaseSchemaEditor                    # isort:skip
 
-DatabaseError = Database.DatabaseError
-IntegrityError = Database.IntegrityError
-
 
 def adapt_datetime_warn_on_aware_datetime(value):
     # Remove this function and rely on the default adapter in Django 2.0.