TST: add rtol and atol to assert_allclose_safely

Allow rtol, atol for wrapper around ``allclose``.

nibabel/testing/__init__.py

@@ -37,7 +37,7 @@ def assert_dt_equal(a, b):
     assert_equal(np.dtype(a).str, np.dtype(b).str)
 
 
-def assert_allclose_safely(a, b, match_nans=True):
+def assert_allclose_safely(a, b, match_nans=True, rtol=1e-5, atol=1e-8):
     """ Allclose in integers go all wrong for large integers
     """
     a = np.atleast_1d(a)  # 0d arrays cannot be indexed
@@ -57,7 +57,7 @@ def assert_allclose_safely(a, b, match_nans=True):
         a = a.astype(float)
     if b.dtype.kind in 'ui':
         b = b.astype(float)
-    assert_true(np.allclose(a, b))
+    assert_true(np.allclose(a, b, rtol=rtol, atol=atol))
 
 
 def assert_re_in(regex, c, flags=0):