bpo-36675: Fix doctest directives comments disappear bug

Doc/library/doctest.rst

@@ -721,7 +721,7 @@ above.
 An example's doctest directives modify doctest's behavior for that single
 example.  Use ``+`` to enable the named behavior, or ``-`` to disable it.
 
-For example, this test passes::
+For example, this test passes:
 
    >>> print(list(range(20))) # doctest: +NORMALIZE_WHITESPACE
    [0,   1,  2,  3,  4,  5,  6,  7,  8,  9,
@@ -730,27 +730,27 @@ For example, this test passes::
 Without the directive it would fail, both because the actual output doesn't have
 two blanks before the single-digit list elements, and because the actual output
 is on a single line.  This test also passes, and also requires a directive to do
-so::
+so:
 
    >>> print(list(range(20))) # doctest: +ELLIPSIS
    [0, 1, ..., 18, 19]
 
 Multiple directives can be used on a single physical line, separated by
-commas::
+commas:
 
    >>> print(list(range(20))) # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
    [0,    1, ...,   18,    19]
 
 If multiple directive comments are used for a single example, then they are
-combined::
+combined:
 
    >>> print(list(range(20))) # doctest: +ELLIPSIS
    ...                        # doctest: +NORMALIZE_WHITESPACE
    [0,    1, ...,   18,    19]
 
 As the previous example shows, you can add ``...`` lines to your example
 containing only directives.  This can be useful when an example is too long for
-a directive to comfortably fit on the same line::
+a directive to comfortably fit on the same line:
 
    >>> print(list(range(5)) + list(range(10, 20)) + list(range(30, 40)))
    ... # doctest: +ELLIPSIS

Misc/NEWS.d/next/Documentation/2019-05-06-15-11-23.bpo-36675.ddGwxG.rst

@@ -0,0 +1 @@
+Fix a doctest detective documentation bug.