diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 6f6772ece31b42ba320ab901adeb11dbed210d06..ee948cfa607e312d2fe325c0b1f0d864d3cfa7fb 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -21,8 +21,6 @@ Python 3 Expensive:
   coverage: '/TOTAL.+ ([0-9]{1,3}%)/'
   variables:
     CODECOV_TOKEN: "895e3bf2-cfd0-45f8-9a14-4b7bd148f76d"
-  # tested on Travis for now, fails with odd, non-reproducible failure
-  allow_failure: true
 
 Python 3 CLI Tool:
   script:
diff --git a/course/utils.py b/course/utils.py
index 1b3ef424cb3239ead79261e763aba65b83236df0..68468fe86ff1020fa7b8e1cdc7bd420fc721de76 100644
--- a/course/utils.py
+++ b/course/utils.py
@@ -1084,8 +1084,13 @@ def csv_data_importable(file_contents, column_idx_list, header_count):
             err_msg += ": "
         err_msg += err_str
 
-        if "line contains NULL byte" in err_str:
+        if "line contains NUL" in err_str:
             err_msg = err_msg.rstrip(".") + ". "
+
+            # This message changed over time.
+            # Make the message uniform to please the tests.
+            err_msg = err_msg.replace("NULL byte", "NUL")
+
             err_msg += _("Are you sure the file is a CSV file other "
                          "than a Microsoft Excel file?")
 
diff --git a/tests/test_grades/test_csv.py b/tests/test_grades/test_csv.py
index 2cc6337a5ebdf249ed3da2d89e3c97154fbf94ff..acbe0cdeedb178ae2ad39405645ea2e171ddf1f6 100644
--- a/tests/test_grades/test_csv.py
+++ b/tests/test_grades/test_csv.py
@@ -413,7 +413,8 @@ class ImportGradesTest(GradesTestMixin, TestCase):
 
     def test_import_file_error(self):
         expected_file_error_msg = (
-            "Error: line contains NUL")
+            "Error: line contains NUL. Are you sure the file is a "
+            "CSV file other than a Microsoft Excel file?")
 
         with open(
                 os.path.join(CSV_PATH, 'test_import_excel_failed.xlsx'),
diff --git a/tests/utils.py b/tests/utils.py
index 294b55346151c20a82fdc785fa99a953ed003334..760e4639f6fb74f2e25f5492593d6af66108d604 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -22,6 +22,13 @@ except ImportError:
     # Since Django >= 2.0 only support PY3
     from unittest import mock  # noqa
 
+    if sys.version_info < (3, 8):
+        # __round__ is missing from MagicMock before Py3.8
+        # https://github.com/python/cpython/pull/6880
+        # Work around this by monkeypatching mock:
+        mock._magics.add("__round__")
+        mock._all_magics = mock._magics | mock._non_defaults
+
 
 # {{{ These are copied (and maybe modified) from django official unit tests
 class BaseEmailBackendTestsMixin(object):