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/tests/test_hush_if_test.py b/test/py/tests/test_hush_if_test.py
index cf4c3ae..8b88425 100644
--- a/test/py/tests/test_hush_if_test.py
+++ b/test/py/tests/test_hush_if_test.py
@@ -95,7 +95,7 @@
 )
 
 def exec_hush_if(u_boot_console, expr, result):
-    '''Execute a shell "if" command, and validate its result.'''
+    """Execute a shell "if" command, and validate its result."""
 
     cmd = 'if ' + expr + '; then echo true; else echo false; fi'
     response = u_boot_console.run_command(cmd)
@@ -103,7 +103,7 @@
 
 @pytest.mark.buildconfigspec('sys_hush_parser')
 def test_hush_if_test_setup(u_boot_console):
-    '''Set up environment variables used during the "if" tests.'''
+    """Set up environment variables used during the "if" tests."""
 
     u_boot_console.run_command('setenv ut_var_nonexistent')
     u_boot_console.run_command('setenv ut_var_exists 1')
@@ -111,13 +111,13 @@
 @pytest.mark.buildconfigspec('sys_hush_parser')
 @pytest.mark.parametrize('expr,result', subtests)
 def test_hush_if_test(u_boot_console, expr, result):
-    '''Test a single "if test" condition.'''
+    """Test a single "if test" condition."""
 
     exec_hush_if(u_boot_console, expr, result)
 
 @pytest.mark.buildconfigspec('sys_hush_parser')
 def test_hush_if_test_teardown(u_boot_console):
-    '''Clean up environment variables used during the "if" tests.'''
+    """Clean up environment variables used during the "if" tests."""
 
     u_boot_console.run_command('setenv ut_var_exists')
 
@@ -126,7 +126,7 @@
 # Of those, only UMS currently allows file removal though.
 @pytest.mark.boardspec('sandbox')
 def test_hush_if_test_host_file_exists(u_boot_console):
-    '''Test the "if test -e" shell command.'''
+    """Test the "if test -e" shell command."""
 
     test_file = u_boot_console.config.result_dir + \
         '/creating_this_file_breaks_u_boot_tests'