- There was no real problem to begin with.

  - The hypothetical problem has been fixed by 5bdc8e1a50c8.

Python/random.c is more then in the 3.6 branch.

Copy and then adapt Python/random.c from default branch. Difference between 3.5
and default branches:

* Python 3.5 only uses getrandom() in non-blocking mode: flags=GRND_NONBLOCK
* If getrandom() fails with EAGAIN: py_getrandom() immediately fails and
  remembers that getrandom() doesn't work.
* Python 3.5 has no _PyOS_URandomNonblock() function: _PyOS_URandom()
  works in non-blocking mode on Python 3.5

In urllib.request, suffixes in no_proxy environment variable with
leading dots could match related hostnames again (e.g. .b.c matches a.b.c).
Patch by Milan Oberkirch.

maintenance issues (cost/benefit).

path in order to avoid maintenance issues.

path and cause maintenance issues (3.6 <-> 3.7, private test suite).

CPython and PyPy use f as the name of the first parameter of
DictReader and DictWriter classes.

Patch by James Salt and Greg Bengeult.

* dev_urandom() now calls py_getentropy(). Prepare the fallback to support
  getentropy() failure and falls back on reading from /dev/urandom.
* Simplify dev_urandom(). pyurandom() is now responsible to call getentropy()
  or getrandom(). Enhance also dev_urandom() and pyurandom() documentation.
* getrandom() is now preferred over getentropy(). The glibc 2.24 now implements
  getentropy() on Linux using the getrandom() syscall.  But getentropy()
  doesn't support non-blocking mode. Since getrandom() is tried first, it's not
  more needed to explicitly exclude getentropy() on Solaris. Replace:
  "if defined(HAVE_GETENTROPY) && !defined(sun)"
  with "if defined(HAVE_GETENTROPY)"
* Enhance py_getrandom() documentation. py_getentropy() now supports ENOSYS,
  EPERM & EINTR