command: handle string without terminal escaped char

Fixes #2810

mitmproxy/command.py

@@ -236,7 +236,10 @@ class CommandManager(mitmproxy.types._CommandBase):
         """
             Execute a command string. May raise CommandError.
         """
+        try:
             parts = list(lexer(cmdstr))
+        except ValueError as e:
+            raise exceptions.CommandError("Command error: %s" % e)
         if not len(parts) >= 1:
             raise exceptions.CommandError("Invalid command: %s" % cmdstr)
         return self.call_strings(parts[0], parts[1:])

test/mitmproxy/test_command.py

@@ -281,6 +281,8 @@ def test_simple():
             c.execute("one.two too many args")
         with pytest.raises(exceptions.CommandError, match="Unknown"):
             c.call("nonexistent")
+        with pytest.raises(exceptions.CommandError, match="No escaped"):
+            c.execute("\\")
 
         c.add("empty", a.empty)
         c.execute("empty")