Factored polling std{out,err} reads into a function

The process to poll for data in the stdout and/or stderr pipes during a
low-level command execution was repetitive. Factoring this out into a
function DRYs out the code.

Signed-off-by: Steve Kuznetsov <skuznets@redhat.com>

lib/ansible/module_utils/basic.py

@@ -2133,6 +2133,15 @@ class AnsibleModule(object):
       else:
           self.fail_json(msg='Could not replace file: %s to %s: %s' % (src, dest, exception))
 
+    def _read_from_pipes(self, rpipes, rfds, file_descriptor):
+        data = b('')
+        if file_descriptor in rfds:
+            data = os.read(file_descriptor.fileno(), 9000)
+            if data == b(''):
+                rpipes.remove(file_descriptor)
+
+        return data
+
     def run_command(self, args, check_rc=False, close_fds=True, executable=None, data=None, binary_data=False, path_prefix=None, cwd=None, use_unsafe_shell=False, prompt_regex=None, environ_update=None, umask=None, encoding='utf-8', errors='surrogate_or_strict'):
         '''
         Execute a command, returns rc, stdout, and stderr.
@@ -2329,17 +2338,9 @@ class AnsibleModule(object):
                 cmd.stdin.close()
 
             while True:
-                rfd, wfd, efd = select.select(rpipes, [], rpipes, 1)
-                if cmd.stdout in rfd:
-                    dat = os.read(cmd.stdout.fileno(), 9000)
-                    stdout += dat
-                    if dat == b(''):
-                        rpipes.remove(cmd.stdout)
-                if cmd.stderr in rfd:
-                    dat = os.read(cmd.stderr.fileno(), 9000)
-                    stderr += dat
-                    if dat == b(''):
-                        rpipes.remove(cmd.stderr)
+                rfds, wfds, efds = select.select(rpipes, [], rpipes, 1)
+                stdout += self._read_from_pipes(rpipes, rfds, cmd.stdout)
+                stderr += self._read_from_pipes(rpipes, rfds, cmd.stderr)
                 # if we're checking for prompts, do it now
                 if prompt_re:
                     if prompt_re.search(stdout) and not data:
@@ -2351,7 +2352,7 @@ class AnsibleModule(object):
                 # only break out if no pipes are left to read or
                 # the pipes are completely read and
                 # the process is terminated
-                if (not rpipes or not rfd) and cmd.poll() is not None:
+                if (not rpipes or not rfds) and cmd.poll() is not None:
                     break
                 # No pipes are left to read but process is not yet terminated
                 # Only then it is safe to wait for the process to be finished