Strange case where yaml.load should error but actually loads

[xi]

>>> yaml.load('-\n-3')
[-3]

Adding a newline actually does produce the desired error:

>>> yaml.load('-\n-3\n')
...
yaml.scanner.ScannerError: while scanning a simple key
  in "<string>", line 2, column 1:
    -3
    ^
could not found expected ':'
  in "<string>", line 3, column 1:
    
    ^

[xi]

Fixed in [354].