Also:
- Drop LANGUAGES variable setting, now ignored by the sagemath build system.
- Drop unused SAGE_CBLAS variable from /usr/bin/sage.
- Do not force the C locale when launching sagemath.
- Allow the user to override SAGE_DEBUG in /usr/bin/sage.
- Add -ecm, -giac, and -latte patches to fix interactions with external tools.
- Add -sigfpe patch from upstream.
- Fix flask_autoindex and flask_openid imports in sagenb.
- Add Education category to the desktop file (bz 1624545).
- Fix SINGULAR_SO variable in /usr/bin/sage (bz 1636759 and 1655248).
- Invoke twistd-2 instead of twistd (bz 1640890).
- Improve jupyter integration (bz 1663165).
- Move existing jupyter integration into the notebook subpackage.
- Require python-jupyter-filesystem instead of owning its directories.
- Drop one more remnant of the F24 to F25 upgrade fixup.
