Reintroduce former public validators for negative contours (but they …

…are not used anymore)
matplotlib · NelleV · Feb 18, 2017 · Feb 7, 2017 · Feb 7, 2017 · Feb 8, 2017
commit 2673585f66e838175b1406b24dd22d898e1d189e
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -530,6 +530,22 @@ def validate_ps_distiller(s):
                                        'top', 'none'])
 validate_fillstylelist = _listify_validator(validate_fillstyle)

+validate_negative_linestyle = ValidateInStrings('negative_linestyle',
+                                                ['solid', 'dashed'],
+                                                ignorecase=True)
+
+
+def validate_negative_linestyle_legacy(s):
+    try:
+        res = validate_negative_linestyle(s)
+        return res
+    except ValueError:
+        dashes = validate_nseq_float(2)(s)
+        warnings.warn("Deprecated negative_linestyle specification; use "
+                      "'solid' or 'dashed'",
+                      mplDeprecation)
+        return (0, dashes)  # (offset, (solid, blank))
+

 def validate_corner_mask(s):
    if s == 'legacy':