Bug 1707270 [wpt PR 28667] - Pywebsocket refactoring, a=testonly

Automatic update from web-platform-tests
Squashed 'tools/third_party/pywebsocket3/' changes from 9db3d29db4..265579a969

265579a969 Expose base.py as a public api. (#28)
cdb83e3152 Add missing r to regular expression (#27)

git-subtree-dir: tools/third_party/pywebsocket3
git-subtree-split: 265579a969e1aec2a6457db7674a9e31fbb7d564

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Merge commit '2a247ac52a4af9f82d50b2f96a43abe5c4629ed3' into HEAD

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update ws_h2_handshake.py to recent pywebsocket

pywebsocket has been refactored to expose some utilities and base class
as part of its public API.
(see GoogleChromeLabs/pywebsocket3#28)

By updating to the newest pywebsocket3 version, we can make
ws_h2_handshake much simpler

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Merge commit 'ec57f8af52fe5e1074ec2de6a5d0d88c4cab257a'

Closes web-platform-tests/wpt#28667.

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wpt-commits: 2a247ac52a4af9f82d50b2f96a43abe5c4629ed3, c3c4473d852203e78c4927408aae0b42f95b7385, ec57f8af52fe5e1074ec2de6a5d0d88c4cab257a, 24fa46db564eb4491e9f84edd3d1a07316cc14c6
wpt-pr: 28667

Author: Arno Renevier

testing/web-platform/tests/tools/third_party/pywebsocket3/mod_pywebsocket/handshake/__init__.py

@@ -38,9 +38,9 @@
 from mod_pywebsocket.handshake import hybi
 # Export AbortedByUserException, HandshakeException, and VersionException
 # symbol from this module.
-from mod_pywebsocket.handshake._base import AbortedByUserException
-from mod_pywebsocket.handshake._base import HandshakeException
-from mod_pywebsocket.handshake._base import VersionException
+from mod_pywebsocket.handshake.base import AbortedByUserException
+from mod_pywebsocket.handshake.base import HandshakeException
+from mod_pywebsocket.handshake.base import VersionException
 
 _LOGGER = logging.getLogger(__name__)