Fix the bug 1892610. There're some syntax errors in the comment of stevedore code.

There is a syntax error in the comment of stevedore code.
For example, in the HookManager class:
    :param on_load_failure_callback: Callback function that will be called when
        a entrypoint can not be loaded.
Here should not be `a entrypoint`, just `an entrypoint` instead.

Fixes: bug #1892610

Change-Id: Ic2aaf5f467bcecaec6adff1ead8e159ae749ac50

stevedore/dispatch.py

@@ -142,7 +142,7 @@ class NameDispatchExtensionManager(DispatchExtensionManager):
         then ignored
     :type invoke_on_load: bool
     :param on_load_failure_callback: Callback function that will be called when
-        a entrypoint can not be loaded. The arguments that will be provided
+        an entrypoint can not be loaded. The arguments that will be provided
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function

stevedore/driver.py

@@ -33,7 +33,7 @@ class DriverManager(NamedExtensionManager):
         is True.
     :type invoke_kwds: dict
     :param on_load_failure_callback: Callback function that will be called when
-        a entrypoint can not be loaded. The arguments that will be provided
+        an entrypoint can not be loaded. The arguments that will be provided
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function
@@ -85,7 +85,7 @@ class DriverManager(NamedExtensionManager):
             and then ignored
         :type propagate_map_exceptions: bool
         :param on_load_failure_callback: Callback function that will
-            be called when a entrypoint can not be loaded. The
+            be called when an entrypoint can not be loaded. The
             arguments that will be provided when this is called (when
             an entrypoint fails to load) are (manager, entrypoint,
             exception)

stevedore/enabled.py

@@ -46,7 +46,7 @@ class EnabledExtensionManager(ExtensionManager):
         then ignored
     :type propagate_map_exceptions: bool
     :param on_load_failure_callback: Callback function that will be called when
-        a entrypoint can not be loaded. The arguments that will be provided
+        an entrypoint can not be loaded. The arguments that will be provided
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function

stevedore/extension.py

@@ -110,7 +110,7 @@ class ExtensionManager(object):
         then ignored
     :type propagate_map_exceptions: bool
     :param on_load_failure_callback: Callback function that will be called when
-        a entrypoint can not be loaded. The arguments that will be provided
+        an entrypoint can not be loaded. The arguments that will be provided
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function
@@ -156,7 +156,7 @@ class ExtensionManager(object):
             are logged and then ignored
         :type propagate_map_exceptions: bool
         :param on_load_failure_callback: Callback function that will
-            be called when a entrypoint can not be loaded. The
+            be called when an entrypoint can not be loaded. The
             arguments that will be provided when this is called (when
             an entrypoint fails to load) are (manager, entrypoint,
             exception)

stevedore/hook.py

@@ -32,7 +32,7 @@ class HookManager(NamedExtensionManager):
         is True.
     :type invoke_kwds: dict
     :param on_load_failure_callback: Callback function that will be called when
-        a entrypoint can not be loaded. The arguments that will be provided
+        an entrypoint can not be loaded. The arguments that will be provided
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function

stevedore/named.py

@@ -46,7 +46,7 @@ class NamedExtensionManager(ExtensionManager):
         then ignored
     :type propagate_map_exceptions: bool
     :param on_load_failure_callback: Callback function that will be called when
-        a entrypoint can not be loaded. The arguments that will be provided
+        an entrypoint can not be loaded. The arguments that will be provided
         when this is called (when an entrypoint fails to load) are
         (manager, entrypoint, exception)
     :type on_load_failure_callback: function
@@ -108,7 +108,7 @@ class NamedExtensionManager(ExtensionManager):
             and then ignored
         :type propagate_map_exceptions: bool
         :param on_load_failure_callback: Callback function that will
-            be called when a entrypoint can not be loaded. The
+            be called when an entrypoint can not be loaded. The
             arguments that will be provided when this is called (when
             an entrypoint fails to load) are (manager, entrypoint,
             exception)