CI: tweak docstring test to avoid repr issues on some system

conftest.py

@@ -4,6 +4,8 @@
 
 import pytest
 from sympy import Add
+import numpy as np
+from IPython import get_ipython
 
 from devito import Eq, configuration, Revolver  # noqa
 from devito.checkpointing import NoopRevolver
@@ -453,3 +455,10 @@ def check_array(array, exp_halo, exp_shape, rotate=False):
 
     assert tuple(array.halo) == exp_halo
     assert tuple(shape) == tuple(exp_shape)
+
+
+# Make Ipython use str for numpy dtypes
+for nptype in [np.int32, np.int64, np.float32, np.float64]:
+    if get_ipython() is not None:
+        formatter = get_ipython().display_formatter.formatters['text/plain']
+        formatter.for_type(nptype, lambda n, p, cycle: p.text("%X" % n))