[CI] Install mercurial

Author: straight-shoota

.circleci/config.yml

@@ -40,6 +40,7 @@ jobs:
     docker:
       - image: crystallang/crystal:latest
     steps:
+      - apt-get update && apt-get install mercurial
       - shards-make-test
 
   test-on-osx:
@@ -50,13 +51,14 @@ jobs:
           steps:
             - run:
                 name: Install Crystal
-                command: brew install crystal
+                command: brew install crystal mercurial
       - shards-make-test
 
   test-on-nightly:
     docker:
       - image: crystallang/crystal:nightly
     steps:
+      - apt-get update && apt-get install mercurial
       - shards-make-test
 
 workflows: