[logging] Mute return_output warning for explorers.

This adds a `warn_return_output` flag to
`cdist.exec.remote.Remote.(run_script|run|_run_command)`.

It defaults to `True` keeping current behaviour except when called from
`cdist.core.explorer.Explorer`.
This way debug logging is significantly cleaner.

Fixes #806

cdist/core/explorer.py

@@ -167,7 +167,8 @@ class Explorer(object):
     def run_global_explorer(self, explorer):
         """Run the given global explorer and return it's output."""
         script = os.path.join(self.remote.global_explorer_path, explorer)
-        return self.remote.run_script(script, env=self.env, return_output=True)
+        return self.remote.run_script(script, env=self.env, return_output=True,
+                                      warn_return_output=False)
 
     # type
 
@@ -229,7 +230,8 @@ class Explorer(object):
         })
         script = os.path.join(self.remote.type_path, cdist_type.explorer_path,
                               explorer)
-        return self.remote.run_script(script, env=env, return_output=True)
+        return self.remote.run_script(script, env=env, return_output=True,
+                                      warn_return_output=False)
 
     def transfer_type_explorers(self, cdist_type):
         """Transfer the type explorers for the given type to the

cdist/exec/remote.py

@@ -219,7 +219,7 @@ class Remote(object):
         self._run_command(command)
 
     def run_script(self, script, env=None, return_output=False, stdout=None,
-                   stderr=None):
+                   stderr=None, warn_return_output=True):
         """Run the given script with the given environment on the remote side.
         Return the output as a string.
 
@@ -232,10 +232,11 @@ class Remote(object):
         command.append(script)
 
         return self.run(command, env=env, return_output=return_output,
-                        stdout=stdout, stderr=stderr)
+                        stdout=stdout, stderr=stderr,
+                        warn_return_output=warn_return_output)
 
     def run(self, command, env=None, return_output=False, stdout=None,
-            stderr=None):
+            stderr=None, warn_return_output=True):
         """Run the given command with the given environment on the remote side.
         Return the output as a string.
 
@@ -269,10 +270,11 @@ class Remote(object):
         else:
             cmd.extend(command)
         return self._run_command(cmd, env=env, return_output=return_output,
-                                 stdout=stdout, stderr=stderr)
+                                 stdout=stdout, stderr=stderr,
+                                 warn_return_output=warn_return_output)
 
     def _run_command(self, command, env=None, return_output=False, stdout=None,
-                     stderr=None):
+                     stderr=None, warn_return_output=True):
         """Run the given command with the given environment.
         Return the output as a string.
 
@@ -280,7 +282,8 @@ class Remote(object):
         assert isinstance(command, (list, tuple)), (
                 "list or tuple argument expected, got: %s" % command)
 
-        if return_output and stdout is not subprocess.PIPE:
+        warn_return_output_applies = warn_return_output and return_output
+        if warn_return_output_applies and stdout is not subprocess.PIPE:
             self.log.debug("return_output is True, ignoring stdout")
 
         close_stdout = False