create tools/tests/run_all.py to run all our Python self-tests within tools

tools/tests/run_all.py

Index: tools/tests/run_all.py
diff --git a/tools/tests/run_all.py b/tools/tests/run_all.py
new file mode 100755
index 0000000000000000000000000000000000000000..6d8b44ea31217888545a7bdbc8119ce8f178d043
--- /dev/null
+++ b/tools/tests/run_all.py
@@ -0,0 +1,20 @@
+#!/usr/bin/python
+
+"""
+Copyright 2013 Google Inc.
+
+Use of this source code is governed by a BSD-style license that can be
+found in the LICENSE file.
+
+Run all self-tests that were written in Python, raising an exception if any
+of them fail.
+"""
+
+import skimage_self_test
+
+def main():
+  """Run all self-tests, raising an exception if any of them fail."""
+  skimage_self_test.main()
+
+if __name__ == '__main__':
+  main()