Fix rcParams validator for dashes.

anntzer · anntzer · commit f5057f48bffe · 2020-05-18T16:44:46.000+02:00
Valid dash-patterns are actually just lists of floats:
```
rcParams["lines.dashed_pattern"] = (1, None)
plt.plot([1, 2], ls="--")
```
throws
```
TypeError: unsupported operand type(s) for +: 'float' and 'NoneType'
```
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -1069,9 +1069,9 @@ def _convert_validator_spec(key, conv):
     "lines.solid_joinstyle": validate_joinstyle,
     "lines.dash_capstyle":   validate_capstyle,
     "lines.solid_capstyle":  validate_capstyle,
-    "lines.dashed_pattern":  validate_nseq_float(allow_none=True),
-    "lines.dashdot_pattern": validate_nseq_float(allow_none=True),
-    "lines.dotted_pattern":  validate_nseq_float(allow_none=True),
+    "lines.dashed_pattern":  validate_floatlist,
+    "lines.dashdot_pattern": validate_floatlist,
+    "lines.dotted_pattern":  validate_floatlist,
     "lines.scale_dashes":    validate_bool,
 
     # marker props
