now detect Python source code encoding only in comment lines.

Changeset c39f42f46a05 left a dangling head on 3.1.

It now always checks, instead of only when the LICENSE file doesn't exist.  It
is also protected by the 'network' resource, and uses a HEAD request since we
are only doing an existence check.

Based on report and initial patch from Germán M. Bravo

Patch by Vlad Shcherbina

Patch contributed by Vajrasky Kok. Addresses Issue #17324

if all necessary functions are already found in libuuid.
Patch by Evgeny Sologubov.

Addresses issue #14927

Patch contributed by Anoop Thomas Mathew.

Addresses issue #18800

Addresses issue #18438

When test.support was converted to a package, it started silently
skipping the tests which needed to download support data to run.

This change refactors the affected code, and also tidies up
test.support.findfile to remove the unused *here* parameter, document
the *subdir* parameter and rename the *filename* parameter to avoid
shadowing the file builtin and be consistent with the documentation.

The unexpected skips were noticed and reported by Zachary Ware

Patch contributed by Olivier Hervieu and Dmi Baranov.

Fixes issue #18206 Patch contributed by  Berker Peksag and py.user

Correct the wrong documentation.

The error caused test_inline_methods() to test much less than intended.
Caught (& fixed) by Armin Rigo.

existing directory caused mkstemp and related APIs to fail instead of
retrying. Report and fix by Vlad Shcherbina.