Description: Allow tests to use the data files in the source tree

We don't ship these in the package,
but do want to run the tests that use them

Author: Rebecca N. Palmer <rebecca_palmer@zoho.com>
Forwarded: https://github.com/pandas-dev/pandas/issues/54907

--- a/pandas/conftest.py
+++ b/pandas/conftest.py
@@ -34,6 +34,7 @@ from typing import (
     TYPE_CHECKING,
     Callable,
 )
+import argparse
 
 from dateutil.tz import (
     tzlocal,
@@ -114,6 +115,7 @@ def pytest_addoption(parser) -> None:
         action="store_false",
         help="Don't fail if a test is skipped for missing data file.",
     )
+    parser.addoption("--deb-data-root-dir", action="store", help=argparse.SUPPRESS)  # for internal use of the Debian CI infrastructure, may change without warning.  Security note: test_pickle can run arbitrary code from this directory
 
 
 def ignore_doctest_warning(item: pytest.Item, path: str, message: str) -> None:
@@ -1098,7 +1100,7 @@ def strict_data_files(pytestconfig):
 
 
 @pytest.fixture
-def datapath(strict_data_files: str) -> Callable[..., str]:
+def datapath(strict_data_files: str, pytestconfig) -> Callable[..., str]:
     """
     Get the path to a data file.
 
@@ -1116,7 +1118,9 @@ def datapath(strict_data_files: str) ->
     ValueError
         If the path doesn't exist and the --no-strict-data-files option is not set.
     """
-    BASE_PATH = os.path.join(os.path.dirname(__file__), "tests")
+    BASE_PATH = pytestconfig.getoption("--deb-data-root-dir", default=None)
+    if BASE_PATH is None:
+        BASE_PATH = os.path.join(os.path.dirname(__file__), "tests")
 
     def deco(*args):
         path = os.path.join(BASE_PATH, *args)
--- a/pandas/tests/util/test_util.py
+++ b/pandas/tests/util/test_util.py
@@ -35,6 +35,7 @@ def test_datapath_missing(datapath):
         datapath("not_a_file")
 
 
+@pytest.mark.xfail(reason="--deb-data-root-dir intentionally breaks this", strict=False)
 def test_datapath(datapath):
     args = ("io", "data", "csv", "iris.csv")
 
--- a/pandas/tests/io/test_pickle.py
+++ b/pandas/tests/io/test_pickle.py
@@ -115,7 +115,7 @@ def test_pickles(datapath):
         pytest.skip("known failure on non-little endian")
 
     # For loop for compat with --strict-data-files
-    for legacy_pickle in Path(__file__).parent.glob("data/legacy_pickle/*/*.p*kl*"):
+    for legacy_pickle in Path(datapath("io", "data", "legacy_pickle")).glob("*/*.p*kl*"):
         legacy_pickle = datapath(legacy_pickle)
 
         data = pd.read_pickle(legacy_pickle)
@@ -627,7 +627,7 @@ def test_pickle_big_dataframe_compressio
 def test_pickle_frame_v124_unpickle_130(datapath):
     # GH#42345 DataFrame created in 1.2.x, unpickle in 1.3.x
     path = datapath(
-        Path(__file__).parent,
+        "io",
         "data",
         "legacy_pickle",
         "1.2.4",
--- a/pandas/tests/io/formats/style/test_html.py
+++ b/pandas/tests/io/formats/style/test_html.py
@@ -44,10 +44,10 @@ def tpl_table(env):
     return env.get_template("html_table.tpl")
 
 
-def test_html_template_extends_options():
+def test_html_template_extends_options(datapath):
     # make sure if templates are edited tests are updated as are setup fixtures
     # to understand the dependency
-    with open("pandas/io/formats/templates/html.tpl", encoding="utf-8") as file:
+    with open(datapath("../io/formats/templates/html.tpl"), encoding="utf-8") as file:
         result = file.read()
     assert "{% include html_style_tpl %}" in result
     assert "{% include html_table_tpl %}" in result
--- a/pandas/tests/io/xml/conftest.py
+++ b/pandas/tests/io/xml/conftest.py
@@ -4,8 +4,8 @@ import pytest
 
 
 @pytest.fixture
-def xml_data_path():
-    return Path(__file__).parent.parent / "data" / "xml"
+def xml_data_path(datapath):
+    return Path(datapath("io", "data", "xml"))
 
 
 @pytest.fixture
--- a/pandas/tests/io/xml/test_xml.py
+++ b/pandas/tests/io/xml/test_xml.py
@@ -487,13 +487,13 @@ def test_empty_string_etree(val):
             read_xml(BytesIO(val), parser="etree")
 
 
-def test_wrong_file_path(parser):
+def test_wrong_file_path(parser, datapath):
     msg = (
         "Passing literal xml to 'read_xml' is deprecated and "
         "will be removed in a future version. To read from a "
         "literal string, wrap it in a 'StringIO' object."
     )
-    filename = os.path.join("data", "html", "books.xml")
+    filename = os.path.join(datapath("io", "data", "html"), "books.xml")
 
     with pytest.raises(
         FutureWarning,
@@ -1358,17 +1358,16 @@ def test_stylesheet_with_etree(kml_cta_r
 
 
 @pytest.mark.parametrize("val", ["", b""])
-def test_empty_stylesheet(val):
+def test_empty_stylesheet(val, datapath):
     pytest.importorskip("lxml")
     msg = (
         "Passing literal xml to 'read_xml' is deprecated and "
         "will be removed in a future version. To read from a "
         "literal string, wrap it in a 'StringIO' object."
     )
-    kml = os.path.join("data", "xml", "cta_rail_lines.kml")
+    kml = datapath("io", "data", "xml", "cta_rail_lines.kml")
 
-    with pytest.raises(FutureWarning, match=msg):
-        read_xml(kml, stylesheet=val)
+    read_xml(kml, stylesheet=val)
 
 
 # ITERPARSE