tools: make yum package installation more reliable

During continuous integration tests, we're seeing quite a lot of
unreliablity when running 'yum install'. The change here is to move to
re-trying a run of 'yum install --downloadonly' for 10 times or until
it succeeds. Then afterwards, running yum install from the cache.

This seems safer in general than just re-trying an install operation,
since we are specifically affected by the download phase failing.

Also present are some flake8 fixes to tools/read-dependencies.

1 files changed, 16 insertions, 1 deletions

diff --git a/tools/run-centos b/tools/run-centos
index e87b2025..d58ef3e8 100755
--- a/tools/run-centos
+++ b/tools/run-centos
@@ -123,7 +123,22 @@ prep() {
         return 0
     fi
     error "Installing prep packages: ${needed}"
-    yum install --assumeyes ${needed}
+    set -- $needed
+    local n max r
+    n=0; max=10;
+    bcmd="yum install --downloadonly --assumeyes --setopt=keepcache=1"
+    while n=$(($n+1)); do
+       error ":: running $bcmd $* [$n/$max]"
+       $bcmd "$@"
+       r=$?
+       [ $r -eq 0 ] && break
+       [ $n -ge $max ] && { error "gave up on $bcmd"; exit $r; }
+       nap=$(($n*5))
+       error ":: failed [$r] ($n/$max). sleeping $nap."
+       sleep $nap
+    done
+    error ":: running yum install --cacheonly --assumeyes $*"
+    yum install --cacheonly --assumeyes "$@"
 }
 
 start_container() {