fix empty bdist_wheel (#1012)

src/Python/package/setup.py

@@ -26,15 +26,23 @@
 
 from setuptools import setup, find_packages
 import glob
+
+# Force platform specific wheel
 try:
     from wheel.bdist_wheel import bdist_wheel as _bdist_wheel
+    # https://stackoverflow.com/a/45150383/1255535
     class bdist_wheel(_bdist_wheel):
         def finalize_options(self):
             _bdist_wheel.finalize_options(self)
             self.root_is_pure = False
 except ImportError:
+    print('Warning: cannot import "wheel" package to build platform-specific wheel')
+    print('Install the "wheel" package to fix this warning')
     bdist_wheel = None
 
+cmdclass = {'bdist_wheel': bdist_wheel} if bdist_wheel is not None else dict()
+
+
 # Read requirements.txt
 with open('requirements.txt', 'r') as f:
     lines = f.readlines()
@@ -86,7 +94,7 @@ def finalize_options(self):
     description=[
         "Open3D is an open-source library that supports rapid development of software that deals with 3D data."
     ],
-    cmdclass={'bdist_wheel': bdist_wheel},
+    cmdclass=cmdclass,
     install_requires=install_requires,
     include_package_data=True,
     data_files=data_files,