subprocess: fix doctests from failing

(at least on linux)

gevent/subprocess.py

@@ -139,16 +139,14 @@ def check_output(*popenargs, **kwargs):
 
     The arguments are the same as for the Popen constructor.  Example:
 
-    >>> check_output(["ls", "-l", "/dev/null"])
-    'crw-rw-rw- 1 root root 1, 3 Oct 18  2007 /dev/null\n'
+    >>> check_output(["ls", "-1", "/dev/null"])
+    '/dev/null\n'
 
     The stdout argument is not allowed as it is used internally.
     To capture standard error in the result, use stderr=STDOUT.
 
-    >>> check_output(["/bin/sh", "-c",
-    ...               "ls -l non_existent_file ; exit 0"],
-    ...              stderr=STDOUT)
-    'ls: non_existent_file: No such file or directory\n'
+    >>> check_output(["/bin/sh", "-c", "echo hello world"], stderr=STDOUT)
+    'hello world\n'
     """
     if 'stdout' in kwargs:
         raise ValueError('stdout argument not allowed, it will be overridden.')