MNT: simplify string comparison

tacaswell · tacaswell · commit 3eeb476faaa5 · 2019-08-19T15:31:00.000-04:00
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -247,8 +247,7 @@ def switch_backend(newbackend):
     # Need to keep a global reference to the backend for compatibility reasons.
     # See https://github.com/matplotlib/matplotlib/issues/6092
     matplotlib.backends.backend = newbackend
-    if not (isinstance(old_backend, str) and
-            old_backend.lower() == newbackend.lower()):
+    if not cbook._str_equal(old_backend, newbackend):
         close("all")
 
 
