Fix and enable logging-format-interpolation lint

.pylintrc

@@ -32,7 +32,6 @@
 #TODO: Enable simplifiable-if-statement
 #TODO: Enable no-self-use
 #TODO: Enable no-member
-#TODO: Enable logging-format-interpolation
 #TODO: Enable dangerous-default-value
 
-disable=missing-docstring,too-few-public-methods,too-many-arguments,no-init,duplicate-code,invalid-name,suppressed-message,locally-disabled,protected-access,no-name-in-module,unused-argument,fixme,wrong-import-order,no-value-for-parameter,cyclic-import,unused-variable,redefined-outer-name,unused-import,too-many-instance-attributes,broad-except,too-many-locals,too-many-lines,redefined-variable-type,next-method-called,import-error,useless-else-on-loop,too-many-return-statements,too-many-nested-blocks,super-init-not-called,simplifiable-if-statement,no-self-use,no-member,logging-format-interpolation,dangerous-default-value
+disable=missing-docstring,too-few-public-methods,too-many-arguments,no-init,duplicate-code,invalid-name,suppressed-message,locally-disabled,protected-access,no-name-in-module,unused-argument,fixme,wrong-import-order,no-value-for-parameter,cyclic-import,unused-variable,redefined-outer-name,unused-import,too-many-instance-attributes,broad-except,too-many-locals,too-many-lines,redefined-variable-type,next-method-called,import-error,useless-else-on-loop,too-many-return-statements,too-many-nested-blocks,super-init-not-called,simplifiable-if-statement,no-self-use,no-member,dangerous-default-value

src/python/grpcio/grpc/_common.py

@@ -92,7 +92,7 @@ def decode(b):
         try:
             return b.decode('utf8')
         except UnicodeDecodeError:
-            logging.exception('Invalid encoding on {}'.format(b))
+            logging.exception('Invalid encoding on %s', b)
             return b.decode('latin1')