bitbake: lib/bb/build: enable access to logger within tasks

In certain circumstances it can be useful to get access to BitBake's
logger within a task; the main example is in OpenEmbedded's image
construction code where we want to be able to check the log file for
errors and warnings, but we don't want to see any errors or warnings
that were emitted through the logger; so we need a way to exclude those.
In order to do this, pass the logger object into the task via a
BB_TASK_LOGGER variable, and add a logging handler class to bb.utils
that can be added to it in order to keep a list of warnings/errors that
have been emitted.

(Bitbake rev: f1cd6fab604f14d8686b1d783cbfe012d923ee42)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/build.py

@@ -562,6 +562,7 @@ def _exec_task(fn, task, d, quieterr):
 
     localdata.setVar('BB_LOGFILE', logfn)
     localdata.setVar('BB_RUNTASK', task)
+    localdata.setVar('BB_TASK_LOGGER', bblogger)
 
     flags = localdata.getVarFlags(task)
 

bitbake/lib/bb/utils.py

@@ -1503,3 +1503,14 @@ def load_plugins(logger, plugins, pluginpath):
                 plugins.append(obj or plugin)
             else:
                 plugins.append(plugin)
+
+
+class LogCatcher(logging.Handler):
+    """Logging handler for collecting logged messages so you can check them later"""
+    def __init__(self):
+        self.messages = []
+        logging.Handler.__init__(self, logging.WARNING)
+    def emit(self, record):
+        self.messages.append(bb.build.logformatter.format(record))
+    def contains(self, message):
+        return (message in self.messages)