test/py: use " for docstrings

Python's coding style docs indicate to use " not ' for docstrings.

test/py has other violations of the coding style docs, since the docs
specify a stranger style than I would expect, but nobody has complained
about those yet:-)

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/py/u_boot_console_exec_attach.py b/test/py/u_boot_console_exec_attach.py
index 0ca9e7c..19520cb 100644
--- a/test/py/u_boot_console_exec_attach.py
+++ b/test/py/u_boot_console_exec_attach.py
@@ -11,15 +11,15 @@
 from u_boot_console_base import ConsoleBase
 
 class ConsoleExecAttach(ConsoleBase):
-    '''Represents a physical connection to a U-Boot console, typically via a
+    """Represents a physical connection to a U-Boot console, typically via a
     serial port. This implementation executes a sub-process to attach to the
     console, expecting that the stdin/out of the sub-process will be forwarded
     to/from the physical hardware. This approach isolates the test infra-
     structure from the user-/installation-specific details of how to
-    communicate with, and the identity of, serial ports etc.'''
+    communicate with, and the identity of, serial ports etc."""
 
     def __init__(self, log, config):
-        '''Initialize a U-Boot console connection.
+        """Initialize a U-Boot console connection.
 
         Args:
             log: A multiplexed_log.Logfile instance.
@@ -27,7 +27,7 @@
 
         Returns:
             Nothing.
-        '''
+        """
 
         # The max_fifo_fill value might need tweaking per-board/-SoC?
         # 1 would be safe anywhere, but is very slow (a pexpect issue?).
@@ -42,7 +42,7 @@
         runner.close()
 
     def get_spawn(self):
-        '''Connect to a fresh U-Boot instance.
+        """Connect to a fresh U-Boot instance.
 
         The target board is reset, so that U-Boot begins running from scratch.
 
@@ -51,7 +51,7 @@
 
         Returns:
             A u_boot_spawn.Spawn object that is attached to U-Boot.
-        '''
+        """
 
         args = [self.config.board_type, self.config.board_identity]
         s = Spawn(['u-boot-test-console'] + args)