#45683 improved dealing with TimeoutError in various places

• No support for Python < 3.10 where socket.timeout is not an alias for TimeoutError. Both TimeoutError and old socket.timeout inherit from OSError, so better to catch that generic exception.
• Not all read() calls were wrapped in try-except blocks, only urlopen().
• Code related to CDash doesn't use any try-except blocks, but incorrectly looks at getcode().