example of failure: https://travis-ci.org/philmd/qemu/jobs/245612939

  $ git submodule update --init --recursive
  [...]
  Submodule 'pixman' (git://anongit.freedesktop.org/pixman) registered for path 'pixman'
  Cloning into 'pixman'...
  fatal: unable to connect to anongit.freedesktop.org:
  anongit.freedesktop.org[0: 131.252.210.161]: errno=Connection timed out
  anongit.freedesktop.org[1: 2610:10:20:722:a800:ff:fe24:61cf]: errno=Network is unreachable
  Clone of 'git://anongit.freedesktop.org/pixman' into submodule path 'pixman' failed
  The command "git submodule update --init --recursive" failed and exited with 1 during .
  Your build has been stopped.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 .travis.yml | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 82c1819c93..196412f5be 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -76,7 +76,7 @@ before_install:
   - if [ "$TRAVIS_OS_NAME" == "osx" ]; then brew update ; fi
   - if [ "$TRAVIS_OS_NAME" == "osx" ]; then brew install libffi gettext glib pixman ; fi
   - wget -O - http://people.linaro.org/~alex.bennee/qemu-submodule-git-seed.tar.xz | tar -xvJ
-  - git submodule update --init --recursive
+  - travis_retry git submodule update --init --recursive
 before_script:
   - ./configure ${CONFIG}
 script:
@@ -119,7 +119,7 @@ matrix:
         - sudo apt-get update -qq
         - sudo apt-get build-dep -qq qemu
         - wget -O - http://people.linaro.org/~alex.bennee/qemu-submodule-git-seed.tar.xz | tar -xvJ
-        - git submodule update --init --recursive
+        - travis_retry git submodule update --init --recursive
     # Plain Trusty Linux User Build
     - env: CONFIG="--disable-system"
       sudo: required
@@ -131,7 +131,7 @@ matrix:
         - sudo apt-get update -qq
         - sudo apt-get build-dep -qq qemu
         - wget -O - http://people.linaro.org/~alex.bennee/qemu-submodule-git-seed.tar.xz | tar -xvJ
-        - git submodule update --init --recursive
+        - travis_retry git submodule update --init --recursive
     # Trusty System build with latest stable clang
     - sudo: required
       addons:
@@ -149,7 +149,7 @@ matrix:
         - travis_retry sudo apt-get install -qq -y clang-3.9
         - sudo apt-get build-dep -qq qemu
         - wget -O - http://people.linaro.org/~alex.bennee/qemu-submodule-git-seed.tar.xz | tar -xvJ
-        - git submodule update --init --recursive
+        - travis_retry git submodule update --init --recursive
       before_script:
         - ./configure ${CONFIG} || cat config.log
     # Trusty Linux User build with latest stable clang
@@ -169,7 +169,7 @@ matrix:
         - travis_retry sudo apt-get install -qq -y clang-3.9
         - sudo apt-get build-dep -qq qemu
         - wget -O - http://people.linaro.org/~alex.bennee/qemu-submodule-git-seed.tar.xz | tar -xvJ
-        - git submodule update --init --recursive
+        - travis_retry git submodule update --init --recursive
       before_script:
         - ./configure ${CONFIG} || cat config.log
     # Using newer GCC with sanitizers
-- 
2.13.3