Changed exception message raised and updated test case

Author: eicchen

pandas/plotting/_matplotlib/core.py

@@ -805,9 +805,6 @@ def _adorn_subplots(self, fig: Figure) -> None:
                     if not isinstance(self.subplots, bool):
                         if len(self.subplots) != len(self.title):
                             raise ValueError(
-                                "The length of `title` must equal the number "
-                                "of subplots if `title` of type `list` "
-                                "and subplots is iterable.\n"
                                 f"The number of titles ({len(self.title)}) must equal "
                                 f"the number of subplots ({len(self.subplots)})."
                             )

pandas/tests/plotting/test_misc.py

@@ -31,6 +31,8 @@
 plt = pytest.importorskip("matplotlib.pyplot")
 cm = pytest.importorskip("matplotlib.cm")
 
+import re
+
 from pandas.plotting._matplotlib.style import get_standard_colors
 
 
@@ -844,12 +846,10 @@ def test_plot_bar_label_count_expected_fail():
     df = DataFrame(
         [(30, 10, 10, 10), (20, 20, 20, 20), (10, 30, 30, 10)], columns=list("ABCD")
     )
-    with pytest.raises(
-        ValueError,
-        match="The length of `title` must equal the number "
-        "of subplots if `title` of type `list` "
-        "and subplots is iterable.\n",
-    ):
+    error_regex = re.escape(
+        "The number of titles (4) must equal the number of subplots (3)."
+    )
+    with pytest.raises(ValueError, match=error_regex):
         df.plot(
             subplots=[("A", "B")],
             kind="bar",