output_difference(): In fancy-diff cases, the way this split expected &

actual output into lines created spurious empty lines at the ends of
each.  Those matched, but the fancy diffs had surprising line counts (1
larger than expected), and tests kept having to slam <BLANKLINE> into the
expected output to account for this.  Using the splitlines() string method
with keepends=True instead accomplishes what was intended directly.

Lib/doctest.py

@@ -1629,8 +1629,8 @@ class OutputChecker:
         # Check if we should use diff.
         if self._do_a_fancy_diff(want, got, optionflags):
             # Split want & got into lines.
-            want_lines = [l+'\n' for l in want.split('\n')]
-            got_lines = [l+'\n' for l in got.split('\n')]
+            want_lines = want.splitlines(True)  # True == keep line ends
+            got_lines = got.splitlines(True)
             # Use difflib to find their differences.
             if optionflags & REPORT_UDIFF:
                 diff = difflib.unified_diff(want_lines, got_lines, n=2)

Lib/test/test_doctest.py

@@ -972,7 +972,7 @@ and actual outputs to be displayed using a unified diff:
     Failed example:
         print '\n'.join('abcdefg')
     Differences (unified diff with -expected +actual):
-        @@ -1,8 +1,8 @@
+        @@ -1,7 +1,7 @@
          a
         -B
         +b
@@ -982,7 +982,6 @@ and actual outputs to be displayed using a unified diff:
          f
          g
         -h
-    <BLANKLINE>
     (1, 1)
 
 The REPORT_CDIFF flag causes failures that involve multi-line expected
@@ -998,7 +997,7 @@ and actual outputs to be displayed using a context diff:
         print '\n'.join('abcdefg')
     Differences (context diff with expected followed by actual):
         ***************
-        *** 1,8 ****
+        *** 1,7 ****
           a
         ! B
           c
@@ -1006,8 +1005,7 @@ and actual outputs to be displayed using a context diff:
           f
           g
         - h
-    <BLANKLINE>
-        --- 1,8 ----
+        --- 1,7 ----
           a
         ! b
           c
@@ -1015,7 +1013,6 @@ and actual outputs to be displayed using a context diff:
         + e
           f
           g
-    <BLANKLINE>
     (1, 1)
 
 
@@ -1040,7 +1037,6 @@ marking, as well as interline differences.
         ?                       ^
         + a b  c d e f g h i   j k l m
         ?     +              ++    ^
-    <BLANKLINE>
     (1, 1)
 
 The REPORT_ONLY_FIRST_FAILURE supresses result output after the first