Fix send2trash packaging error on macOS

Exception:
Traceback (most recent call last):
  File "PyInstaller/loader/pyiboot01_bootstrap.py", line 149, in __init__
  File "ctypes/__init__.py", line 348, in __init__
OSError: dlopen(/Users/tiger-222/projects/nuxeo-drive/dist/ndrive/Foundation, 6): no suitable image found.  Did find:
	/Users/tiger-222/projects/nuxeo-drive/dist/ndrive/Foundation: not a file
	/Users/tiger-222/projects/nuxeo-drive/dist/ndrive/Foundation: not a file

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "nxdrive/__main__.py", line 114, in main
  File "nxdrive/commandline.py", line 481, in handle
  File "nxdrive/commandline.py", line 493, in get_manager
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "/Users/tiger-222/projects/ven36/lib/python3.6/site-packages/PyInstaller/loader/pyimod03_importers.py", line 627, in exec_module
    exec(bytecode, module.__dict__)
  File "nxdrive/manager.py", line 15, in <module>
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "/Users/tiger-222/projects/ven36/lib/python3.6/site-packages/PyInstaller/loader/pyimod03_importers.py", line 627, in exec_module
    exec(bytecode, module.__dict__)
  File "nxdrive/client/local_client.py", line 19, in <module>
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "/Users/tiger-222/projects/ven36/lib/python3.6/site-packages/PyInstaller/loader/pyimod03_importers.py", line 627, in exec_module
    exec(bytecode, module.__dict__)
  File "send2trash/__init__.py", line 12, in <module>
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "/Users/tiger-222/projects/ven36/lib/python3.6/site-packages/PyInstaller/loader/pyimod03_importers.py", line 627, in exec_module
    exec(bytecode, module.__dict__)
  File "send2trash/plat_osx.py", line 17, in <module>
  File "ctypes/__init__.py", line 426, in LoadLibrary
  File "PyInstaller/loader/pyiboot01_bootstrap.py", line 151, in __init__
PyInstallerImportError: Failed to load dynlib/dll '/Users/tiger-222/projects/nuxeo-drive/dist/ndrive/Foundation'. Most probably this dynlib/dll was not found when the application was frozen.