deps!: Remove support for Python 3.8 (#932)

* Remove support for Python 3.8

This commit removes Python 3.8 from the supported versions.
Updates include changes in noxfiles, GitHub workflows, setup.py,
Kokoro configurations, and documentation to reflect Python 3.9
as the minimum supported version.

* Apply follow-up changes for Python 3.8 removal

This commit addresses items missed in the initial Python 3.8 removal:

* Adds `kokoro/presubmit/system-3.9.cfg`.
* Updates example commands in `CONTRIBUTING.rst`.
* Modifies the warning in `pandas_gbq/__init__.py` for Python < 3.9.
* Updates Python versions in `owlbot.py`.
* Removes 3.8-specific line from `samples/snippets/requirements.txt`.
* Populates `testing/constraints-3.9.txt` with correct lower bounds.

* Update pandas_gbq/__init__.py

* Update samples/snippets/noxfile.py

* Update requirements.txt

* Update testing/constraints-3.9.txt

* Update owlbot.py

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: 3 people

.github/sync-repo-settings.yaml

@@ -11,7 +11,6 @@ branchProtectionRules:
     - 'OwlBot Post Processor'
     - 'docs'
     - 'lint'
-    - 'unit (3.8)'
     - 'unit (3.9)'
     - 'unit (3.10)'
     - 'unit (3.11)'
@@ -20,7 +19,6 @@ branchProtectionRules:
     - 'cover'
     - 'Kokoro'
     - 'Samples - Lint'
-    - 'Samples - Python 3.8'
     - 'Samples - Python 3.9'
     - 'Samples - Python 3.10'
     - 'Samples - Python 3.11'

.github/workflows/unittest.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-22.04
     strategy:
       matrix:
-        python: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
+        python: ['3.9', '3.10', '3.11', '3.12', '3.13']
     steps:
     - name: Checkout
       uses: actions/checkout@v4

.kokoro/presubmit/system-3.8.cfg renamed to .kokoro/presubmit/system-3.9.cfg

@@ -3,5 +3,5 @@
 # Only run the following session(s)
 env_vars: {
   key: "NOX_SESSION"
-  value: "system-3.8"
-}
+  value: "system-3.9"
+}

CONTRIBUTING.rst

@@ -22,7 +22,7 @@ In order to add a feature:
   documentation.
 
 - The feature must work fully on the following CPython versions:
-  3.8, 3.9, 3.10, 3.11, 3.12 and 3.13 on both UNIX and Windows.
+  3.9, 3.10, 3.11, 3.12 and 3.13 on both UNIX and Windows.
 
 - The feature must not add unnecessary dependencies (where
   "unnecessary" is of course subjective, but new dependencies should
@@ -148,7 +148,7 @@ Running System Tests
 
   .. note::
 
-      System tests are only configured to run under Python 3.8, 3.9, 3.10, 3.11, 3.12 and 3.13.
+      System tests are only configured to run under Python 3.9, 3.10, 3.11, 3.12 and 3.13.
       For expediency, we do not run them in older versions of Python 3.
 
   This alone will not run the tests. You'll need to change some local
@@ -221,14 +221,12 @@ Supported Python Versions
 
 We support:
 
--  `Python 3.8`_
 -  `Python 3.9`_
 -  `Python 3.10`_
 -  `Python 3.11`_
 -  `Python 3.12`_
 -  `Python 3.13`_
 
-.. _Python 3.8: https://docs.python.org/3.8/
 .. _Python 3.9: https://docs.python.org/3.9/
 .. _Python 3.10: https://docs.python.org/3.10/
 .. _Python 3.11: https://docs.python.org/3.11/
@@ -241,7 +239,7 @@ Supported versions can be found in our ``noxfile.py`` `config`_.
 .. _config: https://github.com/googleapis/python-bigquery-pandas/blob/main/noxfile.py
 
 
-We also explicitly decided to support Python 3 beginning with version 3.8.
+We also explicitly decided to support Python 3 beginning with version 3.9.
 Reasons for this include:
 
 -  Encouraging use of newest versions of Python 3

noxfile.py

@@ -35,7 +35,7 @@
 DEFAULT_PYTHON_VERSION = "3.10"
 
 
-UNIT_TEST_PYTHON_VERSIONS = ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
+UNIT_TEST_PYTHON_VERSIONS = ["3.9", "3.10", "3.11", "3.12", "3.13"]
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     "asyncmock",
@@ -57,7 +57,7 @@
     "3.9": [],
 }
 
-SYSTEM_TEST_PYTHON_VERSIONS = ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
+SYSTEM_TEST_PYTHON_VERSIONS = ["3.9", "3.10", "3.11", "3.12", "3.13"]
 SYSTEM_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     "pytest",

owlbot.py

@@ -35,8 +35,8 @@
 extras = ["tqdm", "geopandas"]
 templated_files = common.py_library(
     default_python_version="3.10",
-    unit_test_python_versions=["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"],
-    system_test_python_versions=["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"],
+    unit_test_python_versions=["3.9", "3.10", "3.11", "3.12", "3.13"],
+    system_test_python_versions=["3.9", "3.10", "3.11", "3.12", "3.13"],
     cov_level=96,
     unit_test_external_dependencies=["freezegun"],
     unit_test_extras=extras,
@@ -57,8 +57,9 @@
         "docs/multiprocessing.rst",
         "noxfile.py",
         "README.rst",
-        # exclude this file as we have an alternate prerelease.cfg
         ".github/workflows/docs.yml",
+        ".github/sync-repo-settings.yaml",
+        # exclude this file as we have an alternate prerelease.cfg
         ".kokoro/presubmit/prerelease-deps.cfg",
         ".kokoro/presubmit/presubmit.cfg",
     ],

pandas_gbq/__init__.py

@@ -11,14 +11,14 @@
 from .gbq import read_gbq, to_gbq  # noqa
 
 sys_major, sys_minor, sys_micro = _versions_helpers.extract_runtime_version()
-if sys_major == 3 and sys_minor in (7, 8):
+if sys_major == 3 and sys_minor < 9:
     warnings.warn(
-        "The python-bigquery library will stop supporting Python 3.7 "
-        "and Python 3.8 in a future major release expected in Q4 2024. "
-        f"Your Python version is {sys_major}.{sys_minor}.{sys_micro}. We "
-        "recommend that you update soon to ensure ongoing support. For "
-        "more details, see: [Google Cloud Client Libraries Supported Python Versions policy](https://cloud.google.com/python/docs/supported-python-versions)",
-        PendingDeprecationWarning,
+        "pandas-gbq no longer supports Python versions older than 3.9. "
+        "Your Python version is "
+        f"{sys_major}.{sys_minor}.{sys_micro}. Please update "
+        "to Python 3.9 or newer to ensure ongoing support. For more details, "
+        "see: https://cloud.google.com/python/docs/supported-python-versions",
+        FutureWarning,
     )
 
 __version__ = pandas_gbq_version.__version__

samples/snippets/requirements.txt

@@ -1,6 +1,5 @@
 google-cloud-bigquery-storage==2.29.1
 google-cloud-bigquery==3.30.0
 pandas-gbq==0.28.0
-pandas===2.0.3; python_version == '3.8'
-pandas==2.2.3; python_version >= '3.9'
-pyarrow==19.0.1; python_version >= '3.9'
+pandas==2.2.3
+pyarrow==19.0.1

setup.py

@@ -85,7 +85,6 @@
         "License :: OSI Approved :: BSD License",
         "Programming Language :: Python",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: 3.11",
@@ -99,7 +98,7 @@
     packages=packages,
     install_requires=dependencies,
     extras_require=extras,
-    python_requires=">=3.8",
+    python_requires=">=3.9",
     include_package_data=True,
     zip_safe=False,
 )