Add get_s3_file method for use in DVLA processing

tests/app/aws/test_s3.py

@@ -0,0 +1,11 @@
+from app.aws.s3 import get_s3_file
+
+
+def test_get_s3_file_makes_correct_call(sample_service, sample_job, mocker):
+    get_s3_mock = mocker.patch('app.aws.s3.get_s3_object')
+    get_s3_file('foo-bucket', 'bar-file.txt')
+
+    get_s3_mock.assert_called_with(
+        'foo-bucket',
+        'bar-file.txt'
+    )