do_trial(): Fix unreachable `DurationError` patterns

I was getting these warnings:

    warning: unreachable pattern
      --> src/trial.rs:41:17
       |
    40 |                 DurationError => return trial_expired(),
       |                 ------------- matches any value
    41 |                 e => {
       |                 ^ unreachable pattern

    warning: unreachable pattern
      --> src/trial.rs:55:9
       |
    54 |         DurationError => trial_expired(),
       |         ------------- matches any value
    55 |         Err(e) => (),
       |         ^^^^^^ unreachable pattern

Wasn't correctly matching the `DurationError`s.

Add an 'error-chain' `ErrorKind` for `DurationError` to make it the same
type as the others matched in the first `match` pattern.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/errors.rs b/src/errors.rs
index f84bb2e..75079e3 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -8,6 +8,7 @@ error_chain! {
         Io(::std::io::Error);
 
         DateCrypt(DateCryptError);
+        Duration(DurationError);
     }
 }