[FLINK-29461][python] Make the test_process_function more stable

This closes apache#21491.

flink-python/pyflink/datastream/tests/test_data_stream.py

@@ -980,24 +980,23 @@ class MyProcessFunction(ProcessFunction):
 
  def process_element(self, value, ctx):
  current_timestamp = ctx.timestamp()
- current_watermark = ctx.timer_service().current_watermark()
- yield "current timestamp: {}, current watermark: {}, current_value: {}"\
- .format(str(current_timestamp), str(current_watermark), str(value))
+ yield "current timestamp: {}, current_value: {}"\
+ .format(str(current_timestamp), str(value))
 
  watermark_strategy = WatermarkStrategy.for_monotonous_timestamps()\
  .with_timestamp_assigner(SecondColumnTimestampAssigner())
  data_stream.assign_timestamps_and_watermarks(watermark_strategy)\
  .process(MyProcessFunction(), output_type=Types.STRING()).add_sink(self.test_sink)
  self.env.execute('test process function')
  results = self.test_sink.get_results()
- expected = ["current timestamp: 1603708211000, current watermark: "
- "-9223372036854775808, current_value: Row(f0=1, f1='1603708211000')",
- "current timestamp: 1603708224000, current watermark: "
- "-9223372036854775808, current_value: Row(f0=2, f1='1603708224000')",
- "current timestamp: 1603708226000, current watermark: "
- "-9223372036854775808, current_value: Row(f0=3, f1='1603708226000')",
- "current timestamp: 1603708289000, current watermark: "
- "-9223372036854775808, current_value: Row(f0=4, f1='1603708289000')"]
+ expected = ["current timestamp: 1603708211000, "
+ "current_value: Row(f0=1, f1='1603708211000')",
+ "current timestamp: 1603708224000, "
+ "current_value: Row(f0=2, f1='1603708224000')",
+ "current timestamp: 1603708226000, "
+ "current_value: Row(f0=3, f1='1603708226000')",
+ "current timestamp: 1603708289000, "
+ "current_value: Row(f0=4, f1='1603708289000')"]
  self.assert_equals_sorted(expected, results)
 
  def test_process_side_output(self):