The “Logo” fonts distribution underwent a restructuring between TeX Live 2013 and 2014 and the same happened to MiKTeX.
The Metafont sources that are listed in CTAN under
<CTAN>/fonts/mflogo/mf were almost all copies of those in
<CTAN>/systems/knuth/dist/lib/ and are now packaged in TeX Live as
Unfortunately, one of the font sources is missing and it is
logosl8.mf (for which another package provides the PFB version). The contents of the file is very short
% 8-point slanted METAFONT logo
% [ heavily borrowed from D. E. Knuth ]
% Copyright (C) 1995--1999 Ulrik Vieth
% This program is free software; you can redistribute it and/or
% modify it under the terms of the LaTeX Project Public License
% as described in lppl.txt in the base LaTeX distribution; either
% version 1 of the License, or (at your option) any later version.
slant := 1/4;
A bug report should be filed to the TeX Live maintainers (MiKTeX should follow) so they do something about the problem. In the meantime, having a
logosl8.mf in the working directory should suffice to get out of the dilemma.
On the other hand, I'd be wary of loading
texlogos, which is undocumented and wrongly written as it uses
As of October 15, 2015, the distribution of the logo fonts has been updated and the hack of keeping
logosl8.mf along with the file is not needed any more (on TeX Live 2015 and later).