Issue when gnomekeyring is present but not the current backend

Issue was identified in the review for the previous
patch for bug 1116302. Took this chance to rename _IOError
to a better name (KeyringIOError)

Change-Id: I321353d519eaebea27617702f92ecafe2052eb8e

novaclient/shell.py

@@ -35,9 +35,11 @@
     HAS_KEYRING = True
     try:
         if isinstance(keyring.get_keyring(), keyring.backend.GnomeKeyring):
-            _IOError = gnomekeyring.IOError
+            KeyringIOError = gnomekeyring.IOError
+        else:
+            KeyringIOError = IOError
     except Exception:
-        _IOError = IOError
+        KeyringIOError = IOError
 except ImportError:
     pass
 
@@ -151,7 +153,7 @@ def management_url(self):
             block = keyring.get_password('novaclient_auth', self._make_key())
             if block:
                 _token, management_url, _tenant_id = block.split('|', 2)
-        except (_IOError, ValueError):
+        except (KeyringIOError, ValueError):
             pass
         return management_url
 
@@ -168,7 +170,7 @@ def auth_token(self):
             block = keyring.get_password('novaclient_auth', self._make_key())
             if block:
                 token, _management_url, _tenant_id = block.split('|', 2)
-        except (_IOError, ValueError):
+        except (KeyringIOError, ValueError):
             pass
         return token
 
@@ -181,7 +183,7 @@ def tenant_id(self):
             block = keyring.get_password('novaclient_auth', self._make_key())
             if block:
                 _token, _management_url, tenant_id = block.split('|', 2)
-        except (_IOError, ValueError):
+        except (KeyringIOError, ValueError):
             pass
         return tenant_id