Drop support for end-of-life Python 3.8 (#3629)

Python 3.8 entered the end-of-life phase on 2024-10-07.
See https://peps.python.org/pep-0569/

This PR removes CI testing for Python 3.8 and relabels
several occurences of 3.8 to 3.9 in the documentation.

.github/workflows/ci.yaml

@@ -10,7 +10,7 @@ jobs:
   main-test-suite:
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.9", "3.10", "3.11", "3.12"]
     runs-on: ubuntu-20.04
     timeout-minutes: 60
 

README.rst

@@ -117,7 +117,7 @@ For Developers
 Requirements
 ============
 
-Parsl is supported in Python 3.8+. Requirements can be found `here <requirements.txt>`_. Requirements for running tests can be found `here <test-requirements.txt>`_.
+Parsl is supported in Python 3.9+. Requirements can be found `here <requirements.txt>`_. Requirements for running tests can be found `here <test-requirements.txt>`_.
 
 Code of Conduct
 ===============

codemeta.json

@@ -191,8 +191,8 @@
         "name": "The Python Package Index",
         "url": "https://pypi.org"
     },
-    "runtimePlatform": "Python 3.8",
+    "runtimePlatform": "Python 3.9",
     "url": "https://github.com/Parsl/parsl",
     "developmentStatus": "active",
-    "programmingLanguage": "Python :: 3.8"
+    "programmingLanguage": "Python :: 3.9"
 }

docs/quickstart.rst

@@ -10,7 +10,7 @@ Installation
 
 Parsl is available on `PyPI <https://pypi.org/project/parsl/>`_ and `conda-forge <https://anaconda.org/conda-forge/parsl>`_. 
 
-Parsl requires Python3.8+ and has been tested on Linux and macOS.
+Parsl requires Python3.9+ and has been tested on Linux and macOS.
 
 
 Installation using Pip
@@ -31,7 +31,7 @@ Installation using Conda
 
 1. Create and activate a new conda environment::
 
-     $ conda create --name parsl_py38 python=3.8
+     $ conda create --name parsl_py38 python=3.9
      $ source activate parsl_py38
 
 2. Install Parsl::

setup.py

@@ -54,7 +54,7 @@
     include_package_data=True,
     package_data={'parsl': ['py.typed']},
     packages=find_packages(),
-    python_requires=">=3.8.0",
+    python_requires=">=3.9.0",
     install_requires=install_requires,
     scripts = ['parsl/executors/high_throughput/process_worker_pool.py',
                'parsl/executors/high_throughput/interchange.py',
@@ -71,7 +71,6 @@
         # Licence, must match with licence above
         'License :: OSI Approved :: Apache Software License',
         # Python versions supported
-        'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
         'Programming Language :: Python :: 3.11',