[PATCH] oeqa/oetest: Improve subprocess error reporting

[Richard Purdie <richard.purdie@linuxfoundation.org>]

Without this, we get to know the command failed and the exit code but 
have no idea how the command failed since we don't get the output by 
default.

This makes it much easier to see what went wrong and stand a chance of 
fixing it.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

diff --git a/meta/lib/oeqa/oetest.py b/meta/lib/oeqa/oetest.py
index 5146312..fe103e8 100644
--- a/meta/lib/oeqa/oetest.py
+++ b/meta/lib/oeqa/oetest.py
@@ -136,6 +136,12 @@ class oeRuntimeTest(oeTest):
             if status != 0:
                 return status
 
+class OETestCalledProcessError(subprocess.CalledProcessError):
+    def __str__(self):
+        return "Command '%s' returned non-zero exit status %d with output %s and stderr %s" % (self.cmd, self.returncode, self.output, self.stderr)
+
+subprocess.CalledProcessError = OETestCalledProcessError
+
 class oeSDKTest(oeTest):
     def __init__(self, methodName='runTest'):
         self.sdktestdir = oeSDKTest.tc.sdktestdir