Is there a reason TransportQueryError doesn't extend TransportError?

I expected all exceptions to be captured by gql.exceptions.TransportError:

from gql.exceptions import TransportError

try:
    ...
except TransportError as e:
    ...

But TransportQueryError extends from Exception:

Line 30 in 2827d88

class TransportQueryError(Exception):

Is this by design?

No, that's not by design, it's a bug.
Thank you for reporting this!