TextIOWrapper: bad error reporting when write() is forbidden

[pitrou]

BPO	5860
Nosy	@pitrou

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2009-04-27.22:27:25.768>
created_at = <Date 2009-04-27.21:36:54.711>
labels = ['type-bug', 'expert-IO']
title = 'TextIOWrapper: bad error reporting when write() is forbidden'
updated_at = <Date 2009-04-27.22:27:25.767>
user = 'https://github.com/pitrou'

bugs.python.org fields:

activity = <Date 2009-04-27.22:27:25.767>
actor = 'benjamin.peterson'
assignee = 'none'
closed = True
closed_date = <Date 2009-04-27.22:27:25.768>
closer = 'benjamin.peterson'
components = ['IO']
creation = <Date 2009-04-27.21:36:54.711>
creator = 'pitrou'
dependencies = []
files = []
hgrepos = []
issue_num = 5860
keywords = []
message_count = 2.0
messages = ['86700', '86704']
nosy_count = 2.0
nosy_names = ['pitrou', 'dsm001']
pr_nums = []
priority = 'critical'
resolution = 'duplicate'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue5860'
versions = ['Python 3.1']

[pitrou]

Opening an existing file in read-only text mode and trying to write to it:

>>> f = open("LICENSE")
>>> f.write("")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
SystemError: null argument to internal routine

Binary files get it right though:

>>> f = open("LICENSE", "rb")
>>> f.write("")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
io.UnsupportedOperation: write

[dsm001]

See also http://bugs.python.org/issue5844 , which contains a patch to test.