Check existing certificate expiration

This disables renewing the cert unless the existing cert will expire
within 20 days.

It doesn't check if the existing cert has the same names as the new cert
would!  This needs to be done.

1 files changed, 1 insertions, 1 deletions

diff --git a/acme-certify.cabal b/acme-certify.cabal
index ac6427a..9a67cb9 100644
--- a/acme-certify.cabal
+++ b/acme-certify.cabal
@@ -30,7 +30,7 @@ executable acme
                        text, HsOpenSSL, optparse-applicative, time,
                        email-validate, network-uri, directory, yaml-config,
                        yaml, unordered-containers, lens, lens-aeson, process,
-                       posix-escape, transformers, resourcet
+                       posix-escape, transformers, resourcet, mtl
   default-language:    Haskell2010
 
 -- test-suite acme-certify-test