Fix FTBFS due to the move of /usr/bin/python into a separate package

See https://fedoraproject.org/wiki/Changes/Move_usr_bin_python_into_separate_package

serd.spec

@@ -2,7 +2,7 @@
 
 Name:           serd
 Version:        0.28.0
-Release:        4%{?dist}
+Release:        5%{?dist}
 Summary:        A lightweight C library for RDF syntax
 
 License:        ISC
@@ -13,6 +13,7 @@ BuildRequires:  doxygen
 BuildRequires:  graphviz
 BuildRequires:  glib2-devel
 BuildRequires:  python2
+BuildRequires:  python2-rpm-macros
 BuildRequires:  gcc
 
 %description
@@ -44,7 +45,7 @@ sed -i -e 's|bld.add_post_fun(autowaf.run_ldconfig)||' wscript
 %build
 export CFLAGS="%{optflags}"
 export LDFLAGS="%{__global_ldflags}"
-./waf configure \
+%{__python2} waf configure \
     --prefix=%{_prefix} \
     --libdir=%{_libdir} \
     --mandir=%{_mandir} \
@@ -52,10 +53,10 @@ export LDFLAGS="%{__global_ldflags}"
     --docdir=%{_docdir} \
     --test \
     --docs 
-./waf build -v %{?_smp_mflags}
+%{__python2} waf build -v %{?_smp_mflags}
 
 %install
-DESTDIR=%{buildroot} ./waf install
+DESTDIR=%{buildroot} %{__python2} waf install
 chmod +x %{buildroot}%{_libdir}/lib%{name}-%{maj}.so.*
 # Move devel docs to the right directory
 install -d %{buildroot}%{_docdir}/%{name}/%{name}-%{maj}
@@ -80,6 +81,9 @@ mv %{buildroot}%{_docdir}/%{name}-%{maj}/html %{buildroot}%{_docdir}/%{name}/%{n
 %{_includedir}/%{name}-%{maj}/
 
 %changelog
+* Sun Jul 15 2018 Guido Aulisi <guido.aulisi@gmail.com> - 0.28.0-5
+- Fix FTBFS due to the move of /usr/bin/python into a separate package
+
 * Sat Jul 14 2018 Fedora Release Engineering <releng@fedoraproject.org> - 0.28.0-4
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_29_Mass_Rebuild