Add srcs_version = "PY2AND3" in BUILD files
The sources themselves appear to already be Python 3 clean.
diff --git a/BUILD b/BUILD
index 97e3f45..ee31cd8 100644
--- a/BUILD
+++ b/BUILD
@@ -512,6 +512,7 @@
py_proto_library(
name = "protobuf_python",
srcs = WELL_KNOWN_PROTOS,
+ srcs_version = "PY2AND3",
include = "src",
protoc = ":protoc",
py_extra_srcs = [":python_srcs"],
@@ -555,6 +556,7 @@
py_library(
name = "python_tests",
srcs = [":python_test_srcs"],
+ srcs_version = "PY2AND3",
deps = [
":protobuf_python",
":python_common_test_protos",