Use double quotes for string values in documentation

Change from single quotes to double quotes when describing string
values like "ignore", "warn", and "fail" in docstrings and
documentation for consistency.

Author: gpshead

Doc/library/multiprocessing.rst

@@ -1222,9 +1222,9 @@ Miscellaneous
    launched (before creating a :class:`Pool` or starting a :class:`Process`).
 
    The *on_error* parameter controls how :exc:`ImportError` exceptions during
-   module preloading are handled: ``'ignore'`` (default) silently ignores
-   failures, ``'warn'`` causes the forkserver subprocess to emit an
-   :exc:`ImportWarning` to stderr, and ``'fail'`` causes the forkserver
+   module preloading are handled: ``"ignore"`` (default) silently ignores
+   failures, ``"warn"`` causes the forkserver subprocess to emit an
+   :exc:`ImportWarning` to stderr, and ``"fail"`` causes the forkserver
    subprocess to exit with the exception traceback on stderr, making
    subsequent process creation fail with :exc:`EOFError` or
    :exc:`ConnectionError`.

Lib/multiprocessing/context.py

@@ -181,8 +181,8 @@ def set_forkserver_preload(self, module_names, *, on_error='ignore'):
         '''Set list of module names to try to load in forkserver process.
 
         The on_error parameter controls how import failures are handled:
-        'ignore' (default) silently ignores failures, 'warn' emits warnings,
-        and 'fail' raises exceptions breaking the forkserver context.
+        "ignore" (default) silently ignores failures, "warn" emits warnings,
+        and "fail" raises exceptions breaking the forkserver context.
         '''
         from .forkserver import set_forkserver_preload
         set_forkserver_preload(module_names, on_error=on_error)

Lib/multiprocessing/forkserver.py

@@ -69,8 +69,8 @@ def set_forkserver_preload(self, modules_names, *, on_error='ignore'):
         '''Set list of module names to try to load in forkserver process.
 
         The on_error parameter controls how import failures are handled:
-        'ignore' (default) silently ignores failures, 'warn' emits warnings,
-        and 'fail' raises exceptions breaking the forkserver context.
+        "ignore" (default) silently ignores failures, "warn" emits warnings,
+        and "fail" raises exceptions breaking the forkserver context.
         '''
         if not all(type(mod) is str for mod in modules_names):
             raise TypeError('module_names must be a list of strings')
@@ -226,7 +226,7 @@ def _handle_preload(preload, main_path=None, sys_path=None, on_error='ignore'):
         preload: List of module names to preload.
         main_path: Path to __main__ module if '__main__' is in preload.
         sys_path: sys.path to use for imports (None means use current).
-        on_error: How to handle import errors ('ignore', 'warn', or 'fail').
+        on_error: How to handle import errors ("ignore", "warn", or "fail").
     """
     if not preload:
         return