Upgrade pip from 1.5.3 to 1.5.4
Issue #20114: Double timeout in test_semaphore_tracker() to reduce
chance of sporadic failures.
Issue #11188, #19748: mktime() returns -1 on error. On Linux, the tm_wday field
is used as a sentinel () to detect if -1 is really an error or a valid
timestamp. On AIX, tm_wday is unchanged even on success and so cannot be used
as a sentinel.
inspect.signature: Check for function-like objects before builtins. Issue #17159