Make parametrize example deterministic

Author: nicoddemus

doc/en/example/parametrize.rst

@@ -346,7 +346,7 @@ parametrizer`_ but in a lot less code::
     def pytest_generate_tests(metafunc):
         # called once per each test function
         funcarglist = metafunc.cls.params[metafunc.function.__name__]
-        argnames = list(funcarglist[0])
+        argnames = sorted(funcarglist[0])
         metafunc.parametrize(argnames, [[funcargs[name] for name in argnames]
                 for funcargs in funcarglist])
 
@@ -397,11 +397,10 @@ is to be run with different sets of arguments for its three arguments:
 Running it results in some skips if we don't have all the python interpreters installed and otherwise runs all combinations (5 interpreters times 5 interpreters times 3 objects to serialize/deserialize)::
 
    . $ pytest -rs -q multipython.py
-   ssssssssssss...ssssssssssss
+   sssssssssssssss.........sss.........sss.........
    ======= short test summary info ========
-   SKIP [12] $REGENDOC_TMPDIR/CWD/multipython.py:23: 'python2.6' not found
-   SKIP [12] $REGENDOC_TMPDIR/CWD/multipython.py:23: 'python3.3' not found
-   3 passed, 24 skipped in 0.12 seconds
+   SKIP [21] $REGENDOC_TMPDIR/CWD/multipython.py:23: 'python2.6' not found
+   27 passed, 21 skipped in 0.12 seconds
 
 Indirect parametrization of optional implementations/imports
 --------------------------------------------------------------------