Run coverage checks with python3 (#4245)

.yamato/com.unity.ml-agents-test.yml

 
     {% if package.name == "com.unity.ml-agents" %}
     # TODO get coverage tests running for extensions too
-    - python ml-agents/tests/yamato/check_coverage_percent.py upm-ci~/test-results/ {{ editor.minCoveragePct }}
+    - python3 ml-agents/tests/yamato/check_coverage_percent.py upm-ci~/test-results/ {{ editor.minCoveragePct }}
     {% endif %}
   artifacts:
     logs:
     - upm-ci project test -u {{ editor.version }} --project-path Project --package-filter {{ package.name }} {{ editor.coverageOptions }}
     {% if package.name == "com.unity.ml-agents" %}
     # TODO get coverage tests running for extensions too
-    - python ml-agents/tests/yamato/check_coverage_percent.py upm-ci~/test-results/ {{ editor.minCoveragePct }}
+    - python3 ml-agents/tests/yamato/check_coverage_percent.py upm-ci~/test-results/ {{ editor.minCoveragePct }}
     {% endif %}
   artifacts:
     logs:

ml-agents/tests/yamato/check_coverage_percent.py

 
 SUMMARY_XML_FILENAME = "Summary.xml"
 
-# Note that this is python2 compatible, since that's currently what's installed on most CI images.
-
 
 def check_coverage(root_dir, min_percentage):
     # Walk the root directory looking for the summary file that
                 pct = float(pct)
                 if pct < min_percentage:
                     print(
-                        "Coverage {} is below the min percentage of {}.".format(
-                            pct, min_percentage
-                        )
+                        f"Coverage {pct} is below the min percentage of {min_percentage}."
-                        "Coverage {} is above the min percentage of {}.".format(
-                            pct, min_percentage
-                        )
+                        f"Coverage {pct} is above the min percentage of {min_percentage}."
                     )
                     sys.exit(0)