Refactor ipautil.run

The ipautil.run function now returns an object with returncode and
output are accessible as attributes.

The stdout and stderr of all commands are logged (unless skip_output is given).

The stdout/stderr contents must be explicitly requested with a keyword
argument, otherwise they are None.
This is because in Python 3, the output needs to be decoded, and that can
fail if it's not decodable (human-readable) text.

The raw (bytes) output is always available from the result object,
as is "leniently" decoded output suitable for logging.

All calls are changed to reflect this.

A use of Popen in cainstance is changed to ipautil.run.

Reviewed-By: Jan Cholasta <jcholast@redhat.com>

ipatests/test_cmdline/test_ipagetkeytab.py

@@ -85,8 +85,11 @@ class test_ipagetkeytab(cmdline_test):
                     "-p", "test/notfound.example.com",
                     "-k", self.keytabname,
                    ]
-        (out, err, rc) = ipautil.run(new_args, stdin=None, raiseonerr=False)
+        result = ipautil.run(new_args, stdin=None, raiseonerr=False,
+                             capture_error=True)
+        err = result.error_output
         assert 'Failed to parse result: PrincipalName not found.\n' in err, err
+        rc = result.returncode
         assert rc > 0, rc
 
     def test_2_run(self):
@@ -107,10 +110,11 @@ class test_ipagetkeytab(cmdline_test):
                     "-k", self.keytabname,
                    ]
         try:
-            (out, err, rc) = ipautil.run(new_args, None)
+            result = ipautil.run(new_args, None, capture_error=True)
             expected = 'Keytab successfully retrieved and stored in: %s\n' % (
                 self.keytabname)
-            assert expected in err, 'Success message not in output:\n%s' % err
+            assert (expected in result.error_output,
+                    'Success message not in output:\n%s' % result.error_output)
         except ipautil.CalledProcessError as e:
             assert (False)