[tex-live] transient error with new LaTeX/inputenc: needed to rebuild formats myself

[jfbu]

Hi,

this morning I got an error with

\documentclass{article}

\usepackage[utf8]{inputenc}

\begin{document}

  % nothing here
  
\end{document}

! LaTeX Error: File `uf8.def' not found.

Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: def)

I had updated the TL2018 pretest minutes before.

(last update was at some unknown date in past)

This disappeared after rebuilding the formats via

fmtutil-sys --all

I wonder why that was necessary,

Best

Jean-François