for consistency; it's awkward to see it as a struct while LexerError as a
.class.

The choice is basically a matter of taste, but I personally think it's
better to be defined as a class as its base is defined as a class, and
these exception structs are not just a trivial set of values.

it's a kind of hack for the convenience of the planned change of this branch,
but the revised name doesn't seem really bad anyway.

this is remaining open point from #2375.  The comment was added at
commit 33a3143c, and it's been the same since the introduction.
Aside from the fact that the sentence is incomplete, IMO the comment doesn't
provide any meaningful information; it's obvious that "the source is not
available" if source_ is NULL.  Even if we complete the sentence by
adding, e.g, "(then) throw InvalidOperation", it still doesn't provide
any additional information than the code itself.

So my decision is to to simply clean it up.

callable() has been removed in Python 3, but was reintroduced in Python 3.2. This fix (check for isinstance(obj, collections.Callable) should make the test work with 3.1 and older versions of 3.

(acked on jabber)

- reduced a line that was 1 character too long
- flipped order of check with isdigit()
- renamed Token::NUMBER_RANGE to Token::NUMBER_OUT_OF_RANGE

- add std:: to strerror calls
- clean up and const_cast long_options array

If omitted the build fails on Solaris complaining that distance is unknown.

Which got accidentally removed in the previous commit