compiler_version: suppress stdout unless command fails

build/compiler_version.py

Index: build/compiler_version.py
diff --git a/build/compiler_version.py b/build/compiler_version.py
index 9132261faea1bee8db7c5f5ac6b2af3d22bec029..f1e5c4722c0469825acc561fc9e636fbb54e299c 100755
--- a/build/compiler_version.py
+++ b/build/compiler_version.py
@@ -18,11 +18,17 @@ def GetVersion(compiler):
   try:
     # Note that compiler could be something tricky like "distcc g++".
     compiler = compiler + " -dumpversion"
-    pipe = subprocess.Popen(compiler, stdout=subprocess.PIPE, shell=True)
-    gcc_output = pipe.communicate()[0]
+    pipe = subprocess.Popen(compiler, shell=True,
+                            stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    gcc_output, gcc_error = pipe.communicate()
+    if pipe.returncode:
+      raise subprocess.CalledProcessError(pipe.returncode, compiler)
+
     result = re.match(r"(\d+)\.(\d+)", gcc_output)
     return result.group(1) + result.group(2)
   except Exception, e:
+    if gcc_error:
+      sys.stderr.write(gcc_error)
     print >> sys.stderr, "compiler_version.py failed to execute:", compiler
     print >> sys.stderr, e
     return ""