Macronize getting versions of Python packages in %check

[skip changelog]

python-tox.spec

@@ -126,9 +126,12 @@ export SETUPTOOLS_SCM_PRETEND_VERSION="%{version}"
 
 %if %{with tests}
 %check
+# A macro that returns a version of the installed Python package, as an RPM v-string, defaults to v"0"
+%define pyversion() v"%(%{python3} -c 'import importlib.metadata as im; print(im.version("%{1}"))' 2>/dev/null || echo 0)"
+
 # Upstream requires virtualenv >= 20.31 for tests, and no longer sets VIRTUALENV_WHEEL.
 # To support environments with older virtualenv, we set it manually:
-%if v"%(%{python3} -c 'import importlib.metadata as im; print(im.version("virtualenv"))' 2>/dev/null || echo 0)" < v"20.31"
+%if %{pyversion virtualenv} < v"20.31"
 export VIRTUALENV_WHEEL=bundle
 %endif
 
@@ -146,7 +149,7 @@ k="${k-}${k+ and }not test_str_convert_ok_py39"
 
 # https://github.com/tox-dev/tox/commit/698f1dd663
 # The tests fail with setuptools < 70.1
-%if v"%(%{python3} -c 'import importlib.metadata as im; print(im.version("setuptools"))' 2>/dev/null || echo 0)" < v"70.1"
+%if %{pyversion setuptools} < v"70.1"
 k="${k-}${k+ and }not test_result_json_sequential"
 k="${k-}${k+ and }not test_setuptools_package"
 k="${k-}${k+ and }not test_skip_develop_mode"