fixup! X wcfs/zeo started to work locally

ZEO4 can have ._addr as either ("host", port) or "path".

lib/zodb.py

@@ -322,10 +322,19 @@ def zstor_2zurl(zstor):
     # ZEO
     if ztype == "ZEO.ClientStorage.ClientStorage":
         u = "zeo://"
-        addr = zstor._addr
-        if len(addr) != 1:
-            raise NotImplementedError("ZEO client has multiple configured servers: %r" % (addr,))
-        addr = addr[0]
+        _addr = zstor._addr
+        addr  = None
+        # ZEO4/3 for backward compatibility accept either a single "address" or single ("host", port) pair
+        # https://github.com/zopefoundation/ZEO/blob/4.2.0b1-49-g47d3fbe8/src/ZEO/zrpc/client.py#L179
+        if zmajor <= 4:
+            if isinstance(_addr, str):
+                addr = _addr
+            elif len(_addr) == 2 and isinstance(_addr[0], str) and isinstance(_addr[1], int):
+                addr = _addr
+        if addr is None:
+            if len(_addr) != 1:
+                raise NotImplementedError("ZEO client has multiple configured servers: %r" % (addr,))
+            addr = _addr[0]
         # addr is either TCP (host,port) or UNIX path
         if isinstance(addr, str):
             u += addr