Use BUILD.bazel file when creating py_library rules of extracted whls (#427)

python/pip_install/extract_wheels/lib/bazel.py

diff --git a/python/pip_install/extract_wheels/lib/bazel.py b/python/pip_install/extract_wheels/lib/bazel.py
index ef0d6e8..0affa20 100644
--- a/python/pip_install/extract_wheels/lib/bazel.py
+++ b/python/pip_install/extract_wheels/lib/bazel.py
@@ -27,7 +27,7 @@
     there may be no Python sources whatsoever (e.g. packages written in Cython: like `pymssql`).
     """
 
-    data_exclude = ["*.whl", "**/*.py", "**/* *", "BUILD", "WORKSPACE"] + pip_data_exclude
+    data_exclude = ["*.whl", "**/*.py", "**/* *", "BUILD.bazel", "WORKSPACE"] + pip_data_exclude
 
     return textwrap.dedent(
         """\
@@ -184,7 +184,7 @@
         '"//%s:%s"' % (sanitise_name(d), WHEEL_FILE_LABEL) for d in whl_deps
     ]
 
-    with open(os.path.join(directory, "BUILD"), "w") as build_file:
+    with open(os.path.join(directory, "BUILD.bazel"), "w") as build_file:
         contents = generate_build_file_contents(
             sanitise_name(whl.name), sanitised_dependencies, sanitised_wheel_file_dependencies, pip_data_exclude
         )

python/pip_install/extract_wheels/lib/whl_filegroup_test.py

diff --git a/python/pip_install/extract_wheels/lib/whl_filegroup_test.py b/python/pip_install/extract_wheels/lib/whl_filegroup_test.py
index a338a14..1209456 100644
--- a/python/pip_install/extract_wheels/lib/whl_filegroup_test.py
+++ b/python/pip_install/extract_wheels/lib/whl_filegroup_test.py
@@ -17,7 +17,7 @@
         )[2:]  # Take off the leading // from the returned label.
         # Assert that the raw wheel ends up in the package.
         self.assertIn(wheel_name, os.listdir(generated_bazel_dir))
-        with open("{}/BUILD".format(generated_bazel_dir)) as build_file:
+        with open("{}/BUILD.bazel".format(generated_bazel_dir)) as build_file:
             build_file_content = build_file.read()
             self.assertIn('filegroup', build_file_content)