Travis CI failed because installing dependencies timed out - github

Question

Travis CI for my Github repo keeps failing and I didn't know why, until I read through the Job log and figured out that many dependencies couldn't be downloaded on their machines.
For example, the xcolor package failed to install:
[20/23, 03:54/04:02] install: xcolor [17k]
Downloading
ftp://tug.org/historic/systems/texlive/2015/tlnet-final/archive/xcolor.tar.xz
did not succeed, please retry.
TLPDB::_install_package: couldn't unpack ftp://tug.org/historic/systems/texlive/2015/tlnet-final/archive/xcolor.tar.xz to /home/travis/texmf
which results in the following error:
Latexmk: Missing input file: 'xcolor.sty' from line
'! LaTeX Error: File `xcolor.sty' not found.'
Latexmk: Log file says no output from latex
Latexmk: For rule 'pdflatex', no output was made
The problem is I'm working on a LaTeX project, and LaTeX environments tend to be huge with lots of supporting packages. Here is the relevant part of my setup.sh, which is already the minimal requirement:
sudo tlmgr install \
xkeyval ifthen amsmath bm \
longtable ctex tabu array \
colortbl berasans graphicx longtable \
etoolbox lastpage amssymb mathrsfs \
multirow xeCJK environ after \
booktabs hyperref epstopdf tabu \
fancyhdr listings amsfonts latexsym \
hhline CJK longtable pifont \
geometry ifpdf bmpsize hologo \
fancybox appendix amsbsy paralist \
tabularx xCJK2uni hologo calc \
fontenc ifxetex xcolor palatino
Can I make sure that all required packages are successfully downloaded & installed before the building phase, say, by letting the server to retry several times? If so, how?

Answer 1

From the Travis docs:
If you are getting network timeouts when trying to download dependencies, either use the built in retry feature of your dependency manager or wrap your install commands in the travis_retry function.
For example, in your .travis.yml:
install: travis_retry pip install myawesomepackage
travis_retry will attempt up three times if the return code is non-zero.