enforce Cython

This falls under pre-generated code, while autotools pregenerated
code is used only in build-time, Cython pregenerated code is
what you get for runtime and there might be vulnerabilities
or bad performance due to that (depends on which Cython version
upstream generated C code). Also upstream had to release 4.1.1
with rebuilt C code with latest Cython due to Py3.7.

Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>

python-lxml.spec

@@ -1,10 +1,8 @@
 %global modname lxml
 
-%bcond_without cython
-
 Name:           python-%{modname}
-Version:        4.1.1
-Release:        1%{?dist}
+Version:        4.0.0
+Release:        2%{?dist}
 Summary:        XML processing library combining libxml2/libxslt with the ElementTree API
 
 License:        BSD
@@ -28,9 +26,7 @@ home page < or see our bug tracker at case you want to use the current ...
 Summary:        %{summary}
 BuildRequires:  python2-devel
 BuildRequires:  python2-setuptools
-%if %{with cython}
 BuildRequires:  python2-Cython
-%endif
 Recommends:     python2-cssselect
 Recommends:     python2-html5lib
 Recommends:     python2-beautifulsoup4
@@ -44,9 +40,7 @@ Python 2 version.
 Summary:        %{summary}
 BuildRequires:  python3-devel
 BuildRequires:  python3-setuptools
-%if %{with cython}
 BuildRequires:  python3-Cython
-%endif
 Recommends:     python3-cssselect
 Recommends:     python3-html5lib
 Recommends:     python3-beautifulsoup4
@@ -60,9 +54,7 @@ Python 3 version.
 %autosetup -n %{modname}-%{version}
 
 %build
-%if %{with cython}
 export WITH_CYTHON=true
-%endif
 %py2_build
 %py3_build