Some warnings had "warning: " at the beginning of their message. Now this
is done consistent for all messages.
Especially in test-check-code-hg.t it is an advantage to see warnings at once
because only exceptions to them are tolerated. It is (almost) as obvious as
before a6180647ea.
The prefix will not remain when a warning is changed to a failure. A change
like a91387a37f will not be necessary anymore.
- old-style classes were only checked for one-letter class names
- add check for new-style classes with empty parent class, because
this is not available in Python 2.4
The Python 'is' operator compares object identity, so it should
definitely not be applied to string or number literals, which Python
implementations are free to represent with a temporary object.
This should catch the following kinds of bogus expressions (examples):
x is 'foo' x is not 'foo'
x is "bar" x is not "bar"
x is 42 x is not 42
x is -36 x is not -36
As originally proposed by Martin Geisler, amended with catching
negative numbers.