Add disclaimer and minimal support to start the sagemath notebook

The sagemath notebook is discontinued and not ported to python3.
  This commit adds patches to make it start, have minimal functionality
and show a disclaimer, explaining to user to use the jupyter notebook.

sagemath.spec

@@ -209,6 +209,9 @@ Patch30:	%{name}-sagetex.patch
 # Fix some path settings in the sage environment
 Patch31:	%{name}-env.patch
 
+# Make notebook minimally function until upstream finally removes it
+Patch32:	%{name}-sagenb-python3.patch
+
 BuildRequires:	4ti2
 BuildRequires:	arb-devel
 BuildRequires:	boost-devel
@@ -873,6 +876,7 @@ popd
 %patch29
 %patch30
 %patch31
+%patch32
 
 sed -e 's|@@SAGE_ROOT@@|%{SAGE_ROOT}|' \
     -e 's|@@SAGE_DOC@@|%{SAGE_DOC}|' \