[cdc_rsync] Add integration tests (#42)

[cdc_rsync] Add integration tests

This CL adds Python integration tests for cdc_rsync. To run the tests,
you need to supply a Linux host and proper configuration for cdc_rsync
to work:

  set CDC_SSH_COMMAND=C:\path\to\ssh.exe <args>
  set CDC_SCP_COMMAND=C:\path\to\scp.exe <args>
  C:\python38\python.exe -m integration_tests.cdc_rsync.all_tests --binary_path=C:\full\path\to\cdc_rsync.exe --user_host=user@host

Ran the tests and made sure they worked.

integration_tests/framework/test_runner.py

@@ -0,0 +1,66 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Lint as: python3
+"""Test runner, adds some sugar around logs to make them easier to read."""
+
+import logging
+import traceback
+import unittest
+
+
+class TestRunner(object):
+  """Runner producing test xml output."""
+
+  def run(self, test):  # pylint: disable=invalid-name
+    result = TestResult()
+    logging.info('Running tests...')
+    test(result)
+    logging.info('\n\n******************* TESTS FINISHED *******************\n')
+    logging.info('Ran %d tests with %d errors and %d failures', result.testsRun,
+                 len(result.errors), len(result.failures))
+    for test_and_stack in result.failures:
+      logging.info('\n\n[  TEST FAILED  ] %s\n', test_and_stack[0])
+      logging.info(
+          '%s', test_and_stack[1].replace('\\\\r',
+                                          '\r').replace('\\\\n', '\n').replace(
+                                              '\\r', '\r').replace('\\n', '\n'))
+
+    return result
+
+
+class TestResult(unittest.TestResult):
+
+  def startTest(self, test):
+    """Called when the given test is about to be run."""
+    logging.info('\n\n===== BEGIN TEST CASE: %s =====\n', test)
+    unittest.TestResult.startTest(self, test)
+
+  def stopTest(self, test):
+    """Called when the given test has been run."""
+    unittest.TestResult.stopTest(self, test)
+    logging.info('\n\n===== END TEST CASE: %s =====\n', test)
+
+  def addError(self, test, err):
+    unittest.TestResult.addError(self, test, err)
+    self._LogFailureInfo(err)
+
+  def addFailure(self, test, err):
+    unittest.TestResult.addFailure(self, test, err)
+    self._LogFailureInfo(err)
+
+  def _LogFailureInfo(self, err):
+    exctype, exc, tb = err
+    detail = ''.join(traceback.format_exception(exctype, exc, tb))
+    logging.error('FAILURE: %s', detail)