add workaround for TravisCI 4MB log limit job termination

.ci/travis.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+# workaround from https://stackoverflow.com/a/26082445 to handle Travis 4MB log limit
+set -e
+
+export PING_SLEEP=30s
+export WORKDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+export BUILD_OUTPUT=$WORKDIR/build.out
+
+touch $BUILD_OUTPUT
+
+dump_output() {
+    echo Tailing the last 1000 lines of output:
+    tail -1000 $BUILD_OUTPUT  
+}
+error_handler() {
+    echo ERROR: An error was encountered with the build.
+    dump_output
+    kill $PING_LOOP_PID
+    exit 1
+}
+# If an error occurs, run our error handler to output a tail of the build
+trap 'error_handler' ERR
+
+# Set up a repeating loop to send some output to Travis.
+
+bash -c "while true; do echo \$(date) - building ...; sleep $PING_SLEEP; done" &
+PING_LOOP_PID=$!
+
+.ci/${MODE}_tests.py >> $BUILD_OUTPUT 2>&1
+
+# The build finished without returning an error so dump a tail of the output
+dump_output
+
+# nicely terminate the ping output loop
+kill $PING_LOOP_PID

.travis.yml

@@ -23,8 +23,10 @@ install:
 
 script:
 - .ci/spawn_reverse_shell.py
-- .ci/${MODE}_tests.py
+- MODE=${MODE} .ci/travis.sh
 
+# Travis has a 4MB log limit (https://github.com/travis-ci/travis-ci/issues/1382), but verbose Mitogen logs run larger than that
+# in order to keep verbosity to debug a build failure, will run with this workaround: https://stackoverflow.com/a/26082445
 
 # To avoid matrix explosion, just test against oldest->newest and
 # newest->oldest in various configuartions.