fix

pygmt/encodings.py

@@ -7,10 +7,11 @@
 >>>
 >>> mappings = charset["symbol"]
 >>>
+>>> undefined = "\ufffd"
 >>> markdown = "| octal | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |\n"
 >>> markdown += "|---|---|---|---|---|---|---|---|---|\n"
 >>> for i in range(0o040, 0o400, 8):
-...     chars = [f'&#x{ord(mappings.get(i, "\ufffd")):04x};' for i in range(i, i + 8)]
+...     chars = [f"&#x{ord(mappings.get(i, undefined)):04x};" for i in range(i, i + 8)]
 ...     if all(c == chars[0] for c in chars):
 ...         continue
 ...     row = f"\\{i:03o}"[:-1] + "x"