Fixed #25949 -- Documented Psycopg2 version requirement for JSONField.

docs/ref/contrib/postgres/fields.txt

@@ -483,8 +483,7 @@ JSONField
     of the JSON which allows indexing. The trade-off is a small additional cost
     on writing to the ``jsonb`` field. ``JSONField`` uses ``jsonb``.
 
-    **As a result, the usage of this field is only supported on PostgreSQL
-    versions at least 9.4**.
+    **As a result, this field requires PostgreSQL ≥ 9.4 and Psycopg2 ≥ 2.5.4**.
 
 Querying JSONField
 ^^^^^^^^^^^^^^^^^^

docs/ref/contrib/postgres/index.txt

@@ -8,7 +8,8 @@ PostgreSQL has a number of features which are not shared by the other databases
 Django supports. This optional module contains model fields and form fields for
 a number of PostgreSQL specific data types.
 
-Psycopg2 2.5 or higher is required.
+Psycopg2 2.5 or higher is required, though we highly recommend using the latest
+release. Some fields require higher versions.
 
 .. note::
     Django is, and will continue to be, a database-agnostic web framework. We