When exporting files with Cyrillic letters, TeXmacs 1.0.2.9 doesn't
\usepackage{babel}. When compiling the exported file with latex
(tetex-latex-2.0-alt2), it produces error messages like:

! Undefined control sequence.
Ю->\cyra 

Adding \usepackage[russian]{babel} to the preamble fixes this problem.

Steps to Reproduce:
1. Create a new buffer in TeXmacs, type a Cyrillic letter into it, export the
document to test.tex.
2. Run 'latex test.tex'.