Description: Don't fail sum test on near-cancelling inputs

Failed in 1.5.3+dfsg-11 after it happened to select an input that
cancelled to ~1e-5 (on i386, so x87 excess precision might be involved)

Author: Rebecca N. Palmer <rebecca_palmer@zoho.com>
Forwarded: no

--- a/pandas/tests/frame/test_reductions.py
+++ b/pandas/tests/frame/test_reductions.py
@@ -344,7 +344,7 @@ class TestDataFrameAnalytics:
             np.sum,
             mixed_float_frame.astype("float32"),
             check_dtype=False,
-            rtol=1e-3,
+            rtol=1e-3, atol=1e-3,
         )
 
         assert_stat_op_calc(