tests: replace pycodestyle with black

Drop pycodestyle for code style checking in favor of black. Black is
much faster, stable PEP8 compliant code style checker offering also
automatic formatting. It aims to be very stable and produce smallest
diffs. It's used by many small and big projects.

Running checkstyle with black takes a few seconds with a terse output.
Thus, test-checkstyle-diff is no longer necessary.

Expand scope of checkstyle to all python files in the repo, replacing
test-checkstyle with checkstyle-python.

Also, fixstyle-python is now available for automatic style formatting.

Note: python virtualenv has been consolidated in test/Makefile,
test/requirements*.txt which will eventually be moved to a central
location.  This is required to simply the automated generation of
docker executor images in the CI.

Type: improvement
Change-Id: I022a326603485f58585e879ac0f697fceefbc9c8
Signed-off-by: Klement Sekera <klement.sekera@gmail.com>
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>
diff --git a/test/test_vpe_api.py b/test/test_vpe_api.py
index 54f7e41..d7d4cc7 100644
--- a/test/test_vpe_api.py
+++ b/test/test_vpe_api.py
@@ -23,33 +23,33 @@
     """TestVpeApi"""
 
     def test_log_dump_default(self):
-        rv = self.vapi.cli('test log notice fib entry this is a test')
+        rv = self.vapi.cli("test log notice fib entry this is a test")
         rv = self.vapi.log_dump()
         if enable_print:
-            print('\n'.join([str(v) for v in rv]))
+            print("\n".join([str(v) for v in rv]))
         self.assertTrue(rv)
 
     def test_log_dump_timestamp_0(self):
-        rv = self.vapi.cli('test log notice fib entry this is a test')
+        rv = self.vapi.cli("test log notice fib entry this is a test")
         rv = self.vapi.log_dump(start_timestamp=0.0)
         if enable_print:
-            print('\n'.join([str(v) for v in rv]))
+            print("\n".join([str(v) for v in rv]))
         self.assertTrue(rv)
 
     def test_log_dump_timestamp_future(self):
-        rv = self.vapi.cli('test log debug fib entry test')
+        rv = self.vapi.cli("test log debug fib entry test")
         rv = self.vapi.log_dump(start_timestamp=time.time() + 60.0)
         if enable_print:
-            print('\n'.join([str(v) for v in rv]))
+            print("\n".join([str(v) for v in rv]))
         self.assertFalse(rv)
 
     def test_show_vpe_system_time(self):
         local_start_time = datetime.datetime.now()
         rv = self.vapi.show_vpe_system_time()
-        self.assertTrue(rv.vpe_system_time > local_start_time -
-                        datetime.timedelta(hours=1.0),
-                        'system times differ by more than an hour.')
+        self.assertTrue(
+            rv.vpe_system_time > local_start_time - datetime.timedelta(hours=1.0),
+            "system times differ by more than an hour.",
+        )
         if enable_print:
-            print('\n'.join([str(v) for v in rv]))
-            print('%r %s' % (rv.vpe_system_time,
-                             rv.vpe_system_time))
+            print("\n".join([str(v) for v in rv]))
+            print("%r %s" % (rv.vpe_system_time, rv.vpe_system_time))