Get additional formats from the DateTimeField input formats, they are…

… the same formats as DATETIME_INPUT_FORMATS but its a bit more clear

observation_portal/common/mixins.py

@@ -1,6 +1,6 @@
 from django_filters import fields, IsoDateTimeFilter
 from django.contrib.auth.mixins import UserPassesTestMixin
-from django.utils import formats
+from django.forms import DateTimeField
 
 
 class ListAsDictMixin(object):
@@ -28,9 +28,8 @@ def test_func(self):
 # Use the CustomIsoDateTimeFilterMixin in a FilterSet. Makes all IsoDateTimeFilters within the FilterSet able to parse
 # ISO 8601 datetimes, as well as all the other usual formats that the DateTimeFilter can do.
 # https://django-filter.readthedocs.io/en/master/ref/fields.html#isodatetimefield
-
 class CustomIsoDateTimeField(fields.IsoDateTimeField):
-    input_formats = [fields.IsoDateTimeField.ISO_8601] + list(formats.get_format_lazy('DATETIME_INPUT_FORMATS'))
+    input_formats = [fields.IsoDateTimeField.ISO_8601] + list(DateTimeField.input_formats)
 
 
 class CustomIsoDateTimeFilterMixin(object):