spec: fix buildrequires for rhel 7/8

because setuptools is so old on rhel

python-gwdatafind-server.spec

@@ -21,6 +21,18 @@ BuildRequires: python3-rpm-macros
 BuildRequires: python%{python3_pkgversion}-setuptools
 BuildRequires: systemd
 
+# these are needed for setuptools to parse the version number
+# out of gwdatafind_server/__init__.py, but only because setuptools
+# is so old on rhel (< 46.4.0, https://github.com/pypa/setuptools/pull/1753)
+%if 0%{?rhel} > 0 && 0%{?rhel} < 9
+BuildRequires: python%{python3_pkgversion}-configobj
+BuildRequires: python%{python3_pkgversion}-flask
+BuildRequires: python%{python3_pkgversion}-ligo-segments
+BuildRequires: python%{python3_pkgversion}-scitokens
+# https://git.ligo.org/computing/packaging/rhel/python-configobj/-/issues/1
+BuildRequires: python%{python3_pkgversion}-six
+%endif
+
 # -- src.rpm
 
 %description