[PATCH] yocto-compat-layer: improve error handling in signature creation

[Patrick Ohly <patrick.ohly@intel.com>]

When "bitbake -k -S none world" failed, the error printed by
yocto-compat-layer.py contained the stack trace multiple times and did not
contain the stderr output from bitbake, making the error hard to understand
and debug:

  INFO: ======================================================================
  INFO: ERROR: test_signatures (common.CommonCompatLayer)
  INFO: ----------------------------------------------------------------------
  INFO: Traceback (most recent call last):
    File "/fast/work/poky/scripts/lib/compatlayer/__init__.py", line 144, in get_signatures
      stderr=subprocess.PIPE)
    File "/usr/lib/python3.4/subprocess.py", line 620, in check_output
      raise CalledProcessError(retcode, process.args, output=output)
  subprocess.CalledProcessError: Command 'bitbake -k -S none world' returned non-zero exit status 1

  During handling of the above exception, another exception occurred:

  Traceback (most recent call last):
    File "/fast/work/poky/scripts/lib/compatlayer/cases/common.py", line 51, in test_signatures
      curr_sigs = get_signatures(self.td['builddir'], failsafe=True)
    File "/fast/work/poky/scripts/lib/compatlayer/__init__.py", line 149, in get_signatures
      raise RuntimeError(msg)
  RuntimeError: Traceback (most recent call last):
    File "/fast/work/poky/scripts/lib/compatlayer/__init__.py", line 144, in get_signatures
      stderr=subprocess.PIPE)
    File "/usr/lib/python3.4/subprocess.py", line 620, in check_output
      raise CalledProcessError(retcode, process.args, output=output)
  subprocess.CalledProcessError: Command 'bitbake -k -S none world' returned non-zero exit status 1

  Loading cache...done.
  Loaded 1328 entries from dependency cache.
  NOTE: Resolving any missing task queue dependencies
  NOTE: Runtime target 'zlib-qat' is unbuildable, removing...
  Missing or unbuildable dependency chain was: ['zlib-qat']
  ...
  Summary: There were 5 ERROR messages shown, returning a non-zero exit code.

The yocto-compat-layer.log was incomplete, it only had the first part
without the command output.

stderr was missing due to stderr=subprocess.PIPE.

Instead of the complicated try/except construct it's better to check
the return code ourselves and raise just a single exception. The
output (both on stderr and in the yocto-compat-layer.log) now is:

  INFO: ======================================================================
  INFO: ERROR: test_signatures (common.CommonCompatLayer)
  INFO: ----------------------------------------------------------------------
  INFO: Traceback (most recent call last):
    File "/fast/work/poky/scripts/lib/compatlayer/cases/common.py", line 51, in test_signatures
      curr_sigs = get_signatures(self.td['builddir'], failsafe=True)
    File "/fast/work/poky/scripts/lib/compatlayer/__init__.py", line 147, in get_signatures
      raise RuntimeError(msg)
  RuntimeError: Generating signatures failed. This might be due to some parse error and/or general layer incompatibilities.
  Command: bitbake -k -S none world
  Output:
  Loading cache...done.
  Loaded 1328 entries from dependency cache.
  NOTE: Resolving any missing task queue dependencies
  ERROR: Nothing PROVIDES 'qat16' (but /fast/work/meta-intel/common/recipes-extended/openssl-qat/openssl-qat_0.4.9-009.bb DEPENDS on or otherwise requires it)
  ERROR: qat16 was skipped: incompatible with machine qemux86 (not in COMPATIBLE_MACHINE)
  ...
  Missing or unbuildable dependency chain was: ['openssl-qat-dev']
  ...
  Summary: There were 5 ERROR messages shown, returning a non-zero exit code.

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
---
 scripts/lib/compatlayer/__init__.py | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/scripts/lib/compatlayer/__init__.py b/scripts/lib/compatlayer/__init__.py
index b3a166aa9ab..a7eb8625310 100644
--- a/scripts/lib/compatlayer/__init__.py
+++ b/scripts/lib/compatlayer/__init__.py
@@ -135,17 +135,15 @@ def get_signatures(builddir, failsafe=False):
 
     sigs = {}
 
-    try:
-        cmd = 'bitbake '
-        if failsafe:
-            cmd += '-k '
-        cmd += '-S none world'
-        output = subprocess.check_output(cmd, shell=True,
-                stderr=subprocess.PIPE)
-    except subprocess.CalledProcessError as e:
-        import traceback
-        exc = traceback.format_exc()
-        msg = '%s\n%s\n' % (exc, e.output.decode('utf-8'))
+    cmd = 'bitbake '
+    if failsafe:
+        cmd += '-k '
+    cmd += '-S none world'
+    p = subprocess.Popen(cmd, shell=True,
+                         stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+    output, _ = p.communicate()
+    if p.returncode:
+        msg = "Generating signatures failed. This might be due to some parse error and/or general layer incompatibilities.\nCommand: %s\nOutput:\n%s" % (cmd, output.decode('utf-8'))
         raise RuntimeError(msg)
     sigs_file = os.path.join(builddir, 'locked-sigs.inc')
 
-- 
2.11.0