Python 2 compat for local requirements

(cherry picked from commit c34610e63cc9b509d324bc0ffb09c100063af74e)

python_appimage/utils/compat.py

@@ -1,4 +1,7 @@
-__all__ = ['decode']
+import sys
+
+
+__all__ = ['decode', 'find_spec', 'isolation_flag']
 
 
 def decode(s):
@@ -8,3 +11,21 @@ def decode(s):
         return s.decode()
     except Exception:
         return str(s)
+
+
+if sys.version_info[0] == 2:
+    from collections import namedtuple
+    import imp
+
+    ModuleSpec = namedtuple('ModuleSpec', ('name', 'origin'))
+
+    def find_spec(name):
+        return ModuleSpec(name, imp.find_module(name)[1])
+
+    isolation_flag = '-sE'
+
+else:
+    import importlib
+    find_spec = importlib.util.find_spec
+
+    isolation_flag = '-I'