test/py: Implement pytest infrastructure

This tool aims to test U-Boot by executing U-Boot shell commands using the
console interface. A single top-level script exists to execute or attach
to the U-Boot console, run the entire script of tests against it, and
summarize the results. Advantages of this approach are:

- Testing is performed in the same way a user or script would interact
  with U-Boot; there can be no disconnect.
- There is no need to write or embed test-related code into U-Boot itself.
  It is asserted that writing test-related code in Python is simpler and
  more flexible that writing it all in C.
- It is reasonably simple to interact with U-Boot in this way.

A few simple tests are provided as examples. Soon, we should convert as
many as possible of the other tests in test/* and test/cmd_ut.c too.

The hook scripts, relay control utilities, and udev rules I use for my
own HW setup are published at https://github.com/swarren/uboot-test-hooks.

See README.md for more details!

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Tested-by: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org> #v3

test/py/test.py

@@ -0,0 +1,32 @@
+#!/usr/bin/env python
+
+# Copyright (c) 2015 Stephen Warren
+# Copyright (c) 2015-2016, NVIDIA CORPORATION. All rights reserved.
+#
+# SPDX-License-Identifier: GPL-2.0
+
+# Wrapper script to invoke pytest with the directory name that contains the
+# U-Boot tests.
+
+import os
+import os.path
+import sys
+
+# Get rid of argv[0]
+sys.argv.pop(0)
+
+# argv; py.test test_directory_name user-supplied-arguments
+args = ["py.test", os.path.dirname(__file__) + "/tests"]
+args.extend(sys.argv)
+
+try:
+    os.execvp("py.test", args)
+except:
+    # Log full details of any exception for detailed analysis
+    import traceback
+    traceback.print_exc()
+    # Hint to the user that they likely simply haven't installed the required
+    # dependencies.
+    print >>sys.stderr, """
+exec(py.test) failed; perhaps you are missing some dependencies?
+See test/py/README.md for the list."""