BUG/API: Catch exceptions in _ipython_display_ (#16132)

We raise an UnserializeableWarning when we fail to generate
the table schema and do not publish a `table_schema` repr.

Author: TomAugspurger

pandas/core/generic.py

@@ -43,6 +43,7 @@
 import pandas.core.algorithms as algos
 import pandas.core.common as com
 import pandas.core.missing as missing
+from pandas.errors import UnserializableWarning
 from pandas.io.formats.printing import pprint_thing
 from pandas.io.formats.format import format_percentiles
 from pandas.tseries.frequencies import to_offset
@@ -138,7 +139,12 @@ def _ipython_display_(self):
         # Series doesn't define _repr_html_ or _repr_latex_
         latex = self._repr_latex_() if hasattr(self, '_repr_latex_') else None
         html = self._repr_html_() if hasattr(self, '_repr_html_') else None
-        table_schema = self._repr_table_schema_()
+        try:
+            table_schema = self._repr_table_schema_()
+        except Exception as e:
+            warnings.warn("Cannot create table schema representation. "
+                          "{}".format(e), UnserializableWarning)
+            table_schema = None
         # We need the inital newline since we aren't going through the
         # usual __repr__. See
         # https://github.com/pandas-dev/pandas/pull/14904#issuecomment-277829277

pandas/errors/__init__.py

@@ -55,3 +55,11 @@ class ParserWarning(Warning):
     one specified by the user due to lack of support or functionality for
     parsing particular attributes of a CSV file with the requsted engine
     """
+
+
+class UnserializableWarning(Warning):
+    """
+    Warnng that is raised when a DataFrame cannot be serialzed.
+
+    .. versionadded:: 0.20.0
+    """

pandas/tests/io/formats/test_printing.py

@@ -5,6 +5,7 @@
 import pandas as pd
 
 from pandas import compat
+from pandas.errors import UnserializableWarning
 import pandas.io.formats.printing as printing
 import pandas.io.formats.format as fmt
 import pandas.util.testing as tm
@@ -177,9 +178,16 @@ def test_publishes_not_implemented(self):
 
         make_patch = self.mock.patch('IPython.display.display')
         opt = pd.option_context('display.html.table_schema', True)
-        with opt, make_patch as mock_display:  # noqa
-            with pytest.raises(NotImplementedError):
+        with opt, make_patch as mock_display:
+            with pytest.warns(UnserializableWarning) as record:
                 df._ipython_display_()
+                args, _ = mock_display.call_args
+                arg, = args  # just one argument
+
+        expected = {'text/plain', 'text/html'}
+        assert set(arg.keys()) == expected
+        assert "orient='table' is not supported for MultiIndex" in (
+            record[-1].message.args[0])
 
     def test_config_on(self):
         df = pd.DataFrame({"A": [1, 2]})