Revert "use attrs directly"

This reverts commit 5b14561ec0c1827744c6d4b5127de7bececabb4d.

src/allmydata/cli/grid_manager.py

@@ -9,7 +9,6 @@ from datetime import (
 )
 
 import click
-import attr
 
 from twisted.python.filepath import (
     FilePath,
@@ -197,7 +196,7 @@ def sign(ctx, name, expiry_days):
             "No storage-server called '{}' exists".format(name)
         )
 
-    certificate_data = json.dumps(attr.asdict(certificate), indent=4)
+    certificate_data = json.dumps(certificate.asdict(), indent=4)
     click.echo(certificate_data)
     if fp is not None:
         next_serial = 0

src/allmydata/grid_manager.py

@@ -26,6 +26,7 @@ from allmydata.util import (
 from attrs import (
     define,
     frozen,
+    asdict,
     Factory,
 )
 
@@ -49,6 +50,9 @@ class SignedCertificate(object):
             signature=data["signature"].encode("ascii")
         )
 
+    def asdict(self):
+        return asdict(self)
+
 
 @frozen
 class _GridManagerStorageServer(object):