limited core to 8.6.*, removed mailgun as incompatible with core 8.6.16 yet

composer.json

@@ -31,7 +31,7 @@
         "drupal/computed_field": "^2.0@beta",
         "drupal/config_split": "^1.4",
         "drupal/console": "^1.0.2",
-        "drupal/core": "^8.6.0",
+        "drupal/core": "8.6.*",
         "drupal/entity_clone": "^1.0",
         "drupal/genpass": "1.x-dev",
         "drupal/login_history": "1.x-dev",

config/sync/core.extension.yml

@@ -80,7 +80,6 @@ module:
   linkit: 0
   locale: 0
   login_history: 0
-  mailgun: 0
   maillog: 0
   mailsystem: 0
   materio_home: 0

config/sync/mailgun.settings.yml

@@ -1,13 +0,0 @@
-api_key: ''
-working_domain: _sender
-debug_mode: false
-test_mode: false
-tracking_opens: ''
-tracking_clicks: ''
-tracking_exception: 'user:password_reset'
-format_filter: plain_text
-use_queue: false
-use_theme: false
-tagging_mailkey: true
-_core:
-  default_config_hash: bMOl3jD7ZuzZMuaUYzyqadr56G486ldo28NYIkK_54g

config/sync/system.mail.yml

@@ -1,6 +1,5 @@
 interface:
   default: maillog
-  mailgun: mailgun
 langcode: fr
 _core:
   default_config_hash: lCmomLfOMrVmswIaFN0SimRdg6H1_a0nU60SauWb2WA