Convert from tox to pytest, avoid xdist on RHEL

Both pytest-xdist and tox are unwanted in RHEL, but using tox even on
Fedora seems to have little gain.

python-alembic.spec

@@ -1,6 +1,6 @@
 Name:             python-alembic
 Version:          1.10.4
-Release:          1%{?dist}
+Release:          2%{?dist}
 Summary:          Database migration tool for SQLAlchemy
 
 # SPDX
@@ -17,6 +17,10 @@ BuildArch:        noarch
 BuildRequires:    help2man
 
 BuildRequires:    python3-devel
+BuildRequires:    python3-pytest
+%if %{undefined rhel}
+BuildRequires:    python3-pytest-xdist
+%endif
 
 %global _description %{expand:
 Alembic is a database migrations tool written by the author of SQLAlchemy. A
@@ -54,7 +58,7 @@ sed -r -i 's/^([[:blank:]]*(black|zimports))\b/# &/' tox.ini
 
 
 %generate_buildrequires
-%pyproject_buildrequires -t -x tz
+%pyproject_buildrequires -x tz
 
 
 %build
@@ -81,7 +85,7 @@ ln -s alembic-%{python3_version}.1 %{buildroot}%{_mandir}/man1/alembic.1
 
 
 %check
-%tox
+%pytest %{?!rhel:-n auto}
 
 
 %files -n python3-alembic -f %{pyproject_files}
@@ -96,6 +100,9 @@ ln -s alembic-%{python3_version}.1 %{buildroot}%{_mandir}/man1/alembic.1
 
 
 %changelog
+* Tue May 23 2023 Yaakov Selkowitz <yselkowi@redhat.com> - 1.10.4-2
+- Convert from tox to pytest, avoid xdist on RHEL
+
 * Tue May 09 2023 Frantisek Zatloukal <fzatlouk@redhat.com> - 1.10.4-1
 - Update to 1.10.4 (closes RHBZ#2170561 )