[arch] fix -> uninstall: not detecting hard requirements properly

bauh/gems/arch/exceptions.py

@@ -1,5 +1,13 @@
+from typing import Optional
+
 
 class PackageNotFoundException(Exception):
 
     def __init__(self, name: str):
         self.name = name
+
+
+class PackageInHoldException(Exception):
+
+    def __init__(self, name: Optional[str] = None):
+        self.name = name