Tolerate decoding errors

Sometimes the charset is just wrong, or it uses a non-standard name. Try
to do something useful in these cases.

mbox2web

@@ -136,8 +136,16 @@ def render_body(msg, extra=None):
         format = ct_params.get("format", "fixed")
         if format == "fixed":
             bodytmpl = jenv.get_template("body_text_plain.html")
+            partbytes = msg.get_payload(decode=True)
+            try:
+                parttext = partbytes.decode(charset, errors="replace")
+            except LookupError as e:
+                # Unknown encoding? Probably win-1252
+                print(e, file=sys.stderr)
+                parttext = partbytes.decode("windows-1252", errors="replace")
+
             context = {
-                "body": msg.get_payload(decode=True).decode(charset)
+                "body": parttext
             }
             return bodytmpl.render(context)
         elif format == "flowed":
@@ -653,7 +661,12 @@ class TextFlowedPart:
         charset = ct_params.get("charset", "iso-8859-1")
         format = ct_params.get("format", "fixed")
         delsp = ct_params.get("delsp", "no") == "yes"
-        raw_text = msg.get_payload(decode=True).decode(charset)
+        charset_map = {
+            "x-mac-roman": "mac_roman",
+        }
+        if charset in charset_map:
+            charset = charset_map[charset]
+        raw_text = msg.get_payload(decode=True).decode(charset, errors="replace")
         raw_lines = raw_text.split("\n")
 
         for rl in raw_lines: