Run examples generation on Travis

This will work as a quick-and-dirty test that the output
generated by the script is readable by dot, at least for the
few examples that are in the tree.

Additionally, make generate-examples.sh find a Python interpreter
(instead of relying on "python") and fail if any step fails.

FIxes #20.

Author: lupino3

.travis.yml

@@ -1,9 +1,14 @@
 language: python
+addons:
+  apt:
+    packages:
+      - graphviz
 python:
   - "2.7"
   - "3.3"
   - "3.4"
   - "3.5"
   - "3.6"
 script:
-  - python -m unittest discover
+  - python -m unittest discover
+  - bash scripts/generate-examples.sh

scripts/generate-examples.sh

@@ -1,16 +1,29 @@
 #!/bin/bash
 
+# Ugly way to get any python interpreter. This is necessary because the script will run
+# both with Python 2.7 and Python 3.x under Travis.
+PYTHONS=$(which python3 python2.7 python)
+PYTHON=$(echo $PYTHONS | cut -d" " -f1)
+
+if [ -z "${PYTHON}" ]; then
+    echo "ERROR: no Python interpreter found."
+    exit 1
+fi
+echo "Using Python interpreter ${PYTHON}"
+
+# Return an error if any of the following commands fails.
+set -e
 echo "example1.cmd, --show-all-calls"
-python3 cmd-call-graph.py --show-all-calls < examples/example1.cmd > examples/example1.dot
+${PYTHON} cmd-call-graph.py --show-all-calls < examples/example1.cmd > examples/example1.dot
 echo
 echo "example1.cmd, --show-all-calls --show-node-stats"
-python3 cmd-call-graph.py --show-all-calls --show-node-stats < examples/example1.cmd > examples/example1-nodestats.dot
+${PYTHON} cmd-call-graph.py --show-all-calls --show-node-stats < examples/example1.cmd > examples/example1-nodestats.dot
 echo
 echo "example1.cmd, without --show-all-calls"
-python3 cmd-call-graph.py < examples/example1.cmd > examples/example1-noshowall.dot
+${PYTHON} cmd-call-graph.py < examples/example1.cmd > examples/example1-noshowall.dot
 echo
 echo "loc.cmd, with --show-node-status and without --show-all-calls"
-python3 cmd-call-graph.py --show-node-stats < examples/loc.cmd > examples/loc.dot
+${PYTHON} cmd-call-graph.py --show-node-stats < examples/loc.cmd > examples/loc.dot
 
 dot -Tpng examples/example1.dot > examples/example1.png
 dot -Tpng examples/example1-nodestats.dot > examples/example1-nodestats.png