incompatible dependencies on bundle update rails

Question

Im attempting to do an upgrade from rails 5.1.5 to 5.2.0 however i'm running into a few dependency issues that seemingly should be fine, for example:

Bundler could not find compatible versions for gem "actionmailer":  
In Gemfile:
exception_notification was resolved to 4.4.0, which depends on
  actionmailer (>= 4.0, < 7)

rails (= 5.2.0) was resolved to 5.2.0, which depends on
  actionmailer (= 5.2.0)

simple_token_authentication (~> 1.0) was resolved to 1.15.1, which depends on
  actionmailer (>= 3.2.6, < 6)

But from my understanding (which i'm more than certain may be wrong) . These should in fact all be compatible. The action mailer version would be 5.2.0 as well which fits into

>= 4.0, < 7
= 5.2.0
>= 3.2.6, < 6

Hopefully i'm missing something simple. Thank you in advance.

Edit to include full error message:

Bundler could not find compatible versions for gem "actionmailer":
  In Gemfile:
    exception_notification was resolved to 4.4.0, which depends on
      actionmailer (>= 4.0, < 7)

    rails (= 5.2.0) was resolved to 5.2.0, which depends on
      actionmailer (= 5.2.0)

    simple_token_authentication (~> 1.0) was resolved to 1.15.1, which depends on
      actionmailer (>= 3.2.6, < 6)

Bundler could not find compatible versions for gem "activemodel":
  In Gemfile:
    draper was resolved to 3.0.1, which depends on
      activemodel-serializers-xml (~> 1.0) was resolved to 1.0.2, which depends on
        activemodel (> 5.x)

    draper was resolved to 3.0.1, which depends on
      activemodel (~> 5.0)

    paperclip (~> 5.0.0) was resolved to 5.0.0, which depends on
      activemodel (>= 4.2.0)

    rails (= 5.2.0) was resolved to 5.2.0, which depends on
      activemodel (= 5.2.0)

    searchkick was resolved to 2.4.0, which depends on
      activemodel (>= 4.1)

    valid_email was resolved to 0.1.0, which depends on
      activemodel

    web-console was resolved to 3.5.1, which depends on
      activemodel (>= 5.0)

Bundler could not find compatible versions for gem "activerecord":
  In Gemfile:
    active_record_slave was resolved to 1.5.0, which depends on
      activerecord (>= 3.0)

    activerecord-import was resolved to 0.24.0, which depends on
      activerecord (>= 3.2)

    activerecord-nulldb-adapter was resolved to 0.4.0, which depends on
      activerecord (>= 2.0.0)

    annotate was resolved to 2.7.5, which depends on
      activerecord (>= 3.2, < 7.0)

    deep_cloneable (~> 2.2.2) was resolved to 2.2.2, which depends on
      activerecord (>= 3.1.0, < 5.2.0)

    oink was resolved to 0.10.1, which depends on
      activerecord

    pghero was resolved to 2.3.0, which depends on
      activerecord (>= 5)

    rails (= 5.2.0) was resolved to 5.2.0, which depends on
      activerecord (= 5.2.0)

    with_advisory_lock was resolved to 4.6.0, which depends on
      activerecord (>= 4.2)

Bundler could not find compatible versions for gem "rack":
  In Gemfile:
    rack (= 2.1.2)

    better_errors was resolved to 2.4.0, which depends on
      rack (>= 0.9.0)

    capybara-webkit was resolved to 1.15.1, which depends on
      capybara (>= 2.3, < 4.0) was resolved to 2.18.0, which depends on
        rack (>= 1.0.0)

    omniauth-salesforce was resolved to 1.0.5, which depends on
      omniauth-oauth2 (~> 1.0) was resolved to 1.5.0, which depends on
        oauth2 (~> 1.1) was resolved to 1.4.0, which depends on
          rack (>= 1.2, < 3)

    omniauth-salesforce was resolved to 1.0.5, which depends on
      omniauth (~> 1.0) was resolved to 1.8.1, which depends on
        rack (>= 1.6.2, < 3)

    omniauth-twitter was resolved to 1.4.0, which depends on
      rack

    turnout was resolved to 2.4.1, which depends on
      rack-accept (~> 0.4) was resolved to 0.4.5, which depends on
        rack (>= 0.4)

    rack-mini-profiler was resolved to 2.0.2, which depends on
      rack (>= 1.2.0)

    draper was resolved to 3.0.1, which depends on
      request_store (~> 1.0) was resolved to 1.4.0, which depends on
        rack (>= 1.4)

    sidekiq (= 6.0.6) was resolved to 6.0.6, which depends on
      rack (~> 2.0)

    turnout was resolved to 2.4.1, which depends on
      rack (>= 1.3, < 3)

Bundler could not find compatible versions for gem "rails":
  In Gemfile:
    rails (= 5.2.0)

    human_attribute_values was resolved to 1.0.1, which depends on
      rails (>= 4.1.8, < 6.0)

    minitest-spec-rails was resolved to 5.4.0, which depends on
      rails (>= 4.1)

    nested_form_fields was resolved to 0.8.2, which depends on
      rails (>= 3.2.0)

    spinjs-rails (~> 1.4) was resolved to 1.4, which depends on
      rails (>= 3.1)

Answer 1

This is the critical line in your error message:

deep_cloneable (~> 2.2.2) was resolved to 2.2.2, which depends on
  activerecord (>= 3.1.0, < 5.2.0)

So, that version of deep_cloneable isn't compatible with rails 5.2.0.

Looking at rubygems.org or the CHANGELOG, you see support was added in version 2.3.2. Therefore you'll need to update to at least this version, or drop the dependency, to use rails 5.2.