fixed memoryerror when coping huge file (#16392)

* fixed

* support both python 2 and 3

lib/ansible/parsing/dataloader.py

@@ -380,11 +380,11 @@ class DataLoader():
 
         try:
             with open(to_bytes(real_path), 'rb') as f:
-                data = f.read()
-                if self._vault.is_encrypted(data):
+                if self._vault.is_encrypted(f):
                     # if the file is encrypted and no password was specified,
                     # the decrypt call would throw an error, but we check first
                     # since the decrypt function doesn't know the file name
+                    data = f.read()
                     if not self._vault_password:
                         raise AnsibleParserError("A vault password must be specified to decrypt %s" % file_path)
 

lib/ansible/parsing/vault/__init__.py

@@ -115,6 +115,12 @@ class VaultLib:
         :returns: True if it is recognized.  Otherwise, False.
         """
 
+        if hasattr(data, 'read'):
+            current_position = data.tell()
+            header_part = data.read(len(b_HEADER))
+            data.seek(current_position)
+            return self.is_encrypted(header_part)
+
         if to_bytes(data, errors='strict', encoding='utf-8').startswith(b_HEADER):
             return True
         return False