gh-76912: Raise OSError from any failure in getpass.getuser() (#29739)

* bpo-32731: Raise OSError from any failure in getpass.getuser()
Previously, if the username was not set in certain environment variables, ImportError escaped on Windows systems, and it was possible for KeyError to escape on other systems if getpwuid() failed.

Doc/library/getpass.rst

@@ -46,7 +46,10 @@ The :mod:`getpass` module provides two functions:
    :envvar:`USER`, :envvar:`!LNAME` and :envvar:`USERNAME`, in order, and
    returns the value of the first one which is set to a non-empty string.  If
    none are set, the login name from the password database is returned on
-   systems which support the :mod:`pwd` module, otherwise, an exception is
-   raised.
+   systems which support the :mod:`pwd` module, otherwise, an :exc:`OSError`
+   is raised.
 
    In general, this function should be preferred over :func:`os.getlogin()`.
+
+   .. versionchanged:: 3.13
+      Previously, various exceptions beyond just :exc:`OSError` were raised.

Doc/whatsnew/3.13.rst

@@ -1032,6 +1032,10 @@ Changes in the Python API
   recomended in the documentation.
   (Contributed by Serhiy Storchaka in :gh:`106672`.)
 
+* An :exc:`OSError` is now raised by :func:`getpass.getuser` for any failure to
+  retrieve a username, instead of :exc:`ImportError` on non-Unix platforms or
+  :exc:`KeyError` on Unix platforms where the password database is empty.
+
 
 Build Changes
 =============

Lib/getpass.py

@@ -156,7 +156,11 @@ def getuser():
 
     First try various environment variables, then the password
     database.  This works on Windows as long as USERNAME is set.
+    Any failure to find a username raises OSError.
 
+    .. versionchanged:: 3.13
+        Previously, various exceptions beyond just :exc:`OSError`
+        were raised.
     """
 
     for name in ('LOGNAME', 'USER', 'LNAME', 'USERNAME'):
@@ -164,9 +168,12 @@ def getuser():
         if user:
             return user
 
-    # If this fails, the exception will "explain" why
+    try:
         import pwd
         return pwd.getpwuid(os.getuid())[0]
+    except (ImportError, KeyError) as e:
+        raise OSError('No username set in the environment') from e
+
 
 # Bind the name getpass to the appropriate function
 try:

Lib/test/test_getpass.py

@@ -26,7 +26,7 @@ class GetpassGetuserTest(unittest.TestCase):
         environ.get.return_value = None
         try:
             getpass.getuser()
-        except ImportError: # in case there's no pwd module
+        except OSError:  # in case there's no pwd module
             pass
         except KeyError:
             # current user has no pwd entry
@@ -47,7 +47,7 @@ class GetpassGetuserTest(unittest.TestCase):
                                  getpass.getuser())
                 getpw.assert_called_once_with(42)
         else:
-            self.assertRaises(ImportError, getpass.getuser)
+            self.assertRaises(OSError, getpass.getuser)
 
 
 class GetpassRawinputTest(unittest.TestCase):

Misc/NEWS.d/next/Library/2021-11-23-22-22-49.bpo-32731.kNOASr.rst

@@ -0,0 +1,3 @@
+:func:`getpass.getuser` now raises :exc:`OSError` for all failures rather
+than :exc:`ImportError` on systems lacking the :mod:`pwd` module or
+:exc:`KeyError` if the password database is empty.