Drop false claims of support Python 3.8 or 3.9

Recent changes (in particular, use of the new "structural pattern
matching" syntax, which was introduced in Python 3.10) were already
incompatible with Python <3.10, but neither the tox settings nor
the project metadata had been updated to reflect this fact.

Fedora 35, the oldest currently supported branch of Fedora, already
ships with Python 3.10 by default, so we don't drop support for any
current Fedora releases.

README.md

@@ -59,4 +59,8 @@ errors when generating spec files with rust2rpm.
 
 ## Testing
 
-Use `python -m pytest -v` or `PYTHONPATH=. pytest -v` in the source tree.
+Invoking `tox` will automatically run the test suite on all python versions
+that should be supported.
+
+Use `python -m pytest -v` or `PYTHONPATH=. pytest -v` in the source tree
+(possibly within a virtualenv) to run the tests manually.

setup.cfg

@@ -14,8 +14,6 @@ classifiers =
     License :: OSI Approved :: MIT License
     Operating System :: POSIX :: Linux
     Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.8
-    Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
     Topic :: Software Development :: Build Tools

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py38,py39,py310,py311
+envlist = py310,py311
 skipsdist = True
 
 [testenv]