Fix basic Django 3.2 incompatibilities

dmoj_install_pymysql.py

@@ -1,4 +1,4 @@
 import pymysql
 
 pymysql.install_as_MySQLdb()
-pymysql.version_info = (1, 3, 13, 'final', 0)
+pymysql.version_info = (1, 4, 0, 'final', 0)

judge/utils/raw_sql.py

@@ -55,7 +55,10 @@ def join_sql_subquery(queryset, subquery, params, join_fields, alias, join_type=
         parent_alias = parent_model._meta.db_table
     else:
         parent_alias = queryset.query.get_initial_alias()
-    queryset.query.external_aliases.add(alias)
+    if isinstance(queryset.query.external_aliases, dict):  # Django 3.x
+        queryset.query.external_aliases[alias] = True
+    else:
+        queryset.query.external_aliases.add(alias)
     join = RawSQLJoin(subquery, params, parent_alias, alias, join_type, FakeJoinField(join_fields), join_type == LOUTER)
     queryset.query.join(join)
     join.table_alias = alias

requirements.txt

@@ -1,11 +1,11 @@
-Django>=2.2,<3
-django_compressor
-django-mptt
+Django>=3.2,<4
+django_compressor>=3
+django-mptt>=0.13
 django-pagedown<2
-django-registration-redux
-django-reversion
+django-registration-redux>=2.10
+django-reversion>=3.0.5,<4
 django-social-share
-django-sortedm2m @ git+https://github.com/DMOJ/django-sortedm2m.git
+django-sortedm2m>=3.1.0
 django-impersonate
 dmoj-wpadmin @ git+https://github.com/DMOJ/dmoj-wpadmin.git
 lxml
@@ -18,13 +18,13 @@ pika
 ua-parser
 pyyaml
 jinja2
-django_jinja
+django_jinja>=2.5.0
 llist
 requests
 django-fernet-fields
 pyotp
 qrcode[pil]
-jsonfield
+jsonfield>=3.0.3
 pymoss
 packaging
 celery