rostertab, common: Use the default arg of os.getenv().

poezio/common.py

@@ -47,7 +47,7 @@ def _is_in_path(command: str, return_abs_path=False) -> Union[bool, str]:
         and *return_abs_path* is True, otherwise False.
 
     """
-    path = os.getenv('PATH') or ''
+    path = os.getenv('PATH', default='')
     for directory in path.split(os.pathsep):
         try:
             if command in os.listdir(directory):

poezio/tabs/rostertab.py

@@ -611,7 +611,7 @@ class RosterInfoTab(Tab):
         n = the_input.get_argument_position()
         if n == complete_number:
             if args[n - 1] == '' or len(args) < n + 1:
-                home = os.getenv('HOME') or '/'
+                home = os.getenv('HOME', default='/')
                 return Completion(
                     the_input.new_completion, [home, '/tmp'], n, quotify=True)
             path_ = Path(args[n])