Add some first f-string issues.

test/failing_examples.py

@@ -138,6 +138,12 @@ FAILING_EXAMPLES = [
     'def x():\n 1\n  2',
     'if 1:\nfoo',
     'if 1: blubb\nif 1:\npass\nTrue and False',
+
+    # f-strings
+    'f"{}"',
+    'f"{\\}"',
+    #'f"{\'\\\'}"',
+    'f"{#}"',
 ]
 
 GLOBAL_NONLOCAL_ERROR = [