使用dateutil 2.2，我无法让tzstr examples正常工作（见下文）。它会抛出错误'str' object has no attribute 'read'。查看代码，它在self.instream.read(1)上失败。我应该通过什么类型的？
In [3]: import dateutil.tz
In [4]: dateutil.tz.tzstr('EST5EDT')
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-4-75889fcde3a9> in <module>()
----> 1 dateutil.tz.tzstr("PST")
/Library/Python/2.7/site-packages/dateutil/tz.pyc in __init__(self, s)
579 self._s = s
580
--> 581 res = parser._parsetz(s)
582 if res is None:
583 raise ValueError("unknown string format")
/Library/Python/2.7/site-packages/dateutil/parser.pyc in _parsetz(tzstr)
923 DEFAULTTZPARSER = _tzparser()
924 def _parsetz(tzstr):
--> 925 return DEFAULTTZPARSER.parse(tzstr)
926
927
/Library/Python/2.7/site-packages/dateutil/parser.pyc in parse(self, tzstr)
770 def parse(self, tzstr):
771 res = self._result()
--> 772 l = _timelex.split(tzstr)
773 try:
774
/Library/Python/2.7/site-packages/dateutil/parser.pyc in split(cls, s)
148
149 def split(cls, s):
--> 150 return list(cls(s))
151 split = classmethod(split)
152
/Library/Python/2.7/site-packages/dateutil/parser.pyc in next(self)
145
146 def next(self):
--> 147 return self.__next__() # Python 2.x support
148
149 def split(cls, s):
/Library/Python/2.7/site-packages/dateutil/parser.pyc in __next__(self)
139
140 def __next__(self):
--> 141 token = self.get_token()
142 if token is None:
143 raise StopIteration
/Library/Python/2.7/site-packages/dateutil/parser.pyc in get_token(self)
70 nextchar = self.charstack.pop(0)
71 else:
---> 72 nextchar = self.instream.read(1)
73 while nextchar == '\x00':
74 nextchar = self.instream.read(1)
AttributeError: 'str' object has no attribute 'read'