Egregious Python Type Violations

requests.exceptions.ConnectionError inherits from requests.exceptions.RequestException, which in turn inherits from IOError which in turn inherits from EnvironmentError. EnvironmentError is described as containing a 2-tuple value: on element 0, errno and on element 1, strerror (presumably a string description of the error). For example:

try:
    f = open("/foo")
except IOError as e:
    print("errno: %s" % e.errno)
    print("strerror: %s" % e.strerror)

However, requests seems to take this concept of the 2-tuple errno/strerror pair to the extreme. Instead of an integer and string, a ConnectionError gets as its pair a requests.package.urllib3.exceptions.ProtocolError on element 0 and None on element 1. ProtocolError similarly violates the errno/strerror tuple promise, setting a string on element 0 and a socket.gaierror on element 1. Neither ConnectionError nor ProtocolError set their errno or strerror attributes, so to actually get a string description of a ConnectionError returned by requests, we have to access the args attribute directly: e.args[0].args[0] (or more cryptically: e[0][0]). Don’t forget to except the inevitable IndexError inside your except block for when indexes change out from under you without warning.