HADOOP-16764. Rewrite Python example codes using Python3

[sekikn]

No description provided.

[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	1m 26s	Docker mode activated.
		_ Prechecks _
+1 💚	dupname	0m 0s	No case conflicting files found.
+0 🆗	markdownlint	0m 0s	markdownlint was not available.
+1 💚	@author	0m 0s	The patch does not contain any @author tags.
		_ trunk Compile Tests _
+0 🆗	mvndep	1m 12s	Maven dependency ordering for branch
+1 💚	mvninstall	20m 32s	trunk passed
+1 💚	mvnsite	1m 40s	trunk passed
+1 💚	shadedclient	37m 12s	branch has no errors when building and testing our client artifacts.
		_ Patch Compile Tests _
+0 🆗	mvndep	0m 21s	Maven dependency ordering for patch
+1 💚	mvninstall	1m 12s	the patch passed
+1 💚	mvnsite	1m 27s	the patch passed
+1 💚	whitespace	0m 0s	The patch has no whitespace issues.
+1 💚	shadedclient	14m 33s	patch has no errors when building and testing our client artifacts.
		_ Other Tests _
+1 💚	asflicense	0m 29s	The patch does not generate ASF License warnings.
		58m 23s

Subsystem	Report/Notes
Docker	Client=19.03.5 Server=19.03.5 base: https://builds.apache.org/job/hadoop-multibranch/job/PR-1762/1/artifact/out/Dockerfile
GITHUB PR	#1762
Optional Tests	dupname asflicense mvnsite markdownlint
uname	Linux 4039ffa2bb08 4.15.0-70-generic #79-Ubuntu SMP Tue Nov 12 10:36:11 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	personality/hadoop.sh
git revision	trunk / 72aee11
Max. process+thread count	293 (vs. ulimit of 5500)
modules	C: hadoop-common-project/hadoop-common hadoop-tools/hadoop-streaming U: .
Console output	https://builds.apache.org/job/hadoop-multibranch/job/PR-1762/1/console
versions	git=2.7.4 maven=3.3.9
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[aajisaka]

+1