attempt fixes for pip installable

src/gam/__main__.py

@@ -30,7 +30,7 @@ from gam import controlflow
 import gam
 
 
-def main(argv):
+def main():
     freeze_support()
     if sys.platform == 'darwin':
         # https://bugs.python.org/issue33725 in Python 3.8.0 seems
@@ -47,4 +47,4 @@ def main(argv):
 
 # Run from command line
 if __name__ == '__main__':
-    main(sys.argv)
+    main()

src/setup.cfg

@@ -24,14 +24,14 @@ packages = find:
 python_requires = >=3.6
 install_requires =
     cryptography
-    distro
+    distro; sys_platform == 'linux'
     filelock
     google-api-python-client >= 2.1
     google-auth-httplib2
     google-auth-oauthlib >= 0.4.1
     google-auth >= 1.11.2
     httplib2 >= 0.17.0
-    importlib.metadata
+    importlib.metadata; python_version < '3.8'
     passlib >= 1.7.2
     python-dateutil
     yubikey-manager >= 4.0.0