Customer Register - Identify Existing Email - shopify

Question

I'm trying on Shopify when a user is trying to create an account, to verify if the email that the user picked already exists, the theme I'm using is Debut. So far I've had 0 success with this.
<div class="page-width">
<div class="grid">
<div class="grid__item medium-up--one-half medium-up--push-one-quarter">
<div class="input-form form-vertical">
{% form 'create_customer' %}
<h1 class="text-center">{{ 'customer.register.title' | t }}</h1>
{%- if form.errors -%}
<div class="form-message form-message--error">
{{ form.errors | default_errors }}
</div>
{%- endif -%}
<label for="FirstName">{{ 'customer.register.first_name' | t }}</label>
<input type="text" name="customer[first_name]" id="FirstName" {% if form.first_name %}value="{{ form.first_name }}"{% endif %} autofocus>
<label for="LastName">{{ 'customer.register.last_name' | t }}</label>
<input type="text" name="customer[last_name]" id="LastName" {% if form.last_name %}value="{{ form.last_name }}"{% endif %}>
<label for="Email">{{ 'customer.register.email' | t }}</label>
<input type="email" name="customer[email]" id="Email" class="{% if form.errors contains 'email' %} input--error{% endif %}" {% if form.email %} value="{{ form.email }}"{% endif %} autocorrect="off" autocapitalize="off">
<label for="CreatePassword">{{ 'customer.register.password' | t }}</label>
<input type="password" name="customer[password]" id="CreatePassword" class="{% if form.errors contains 'password' %} input--error{% endif %}">
<label for="CreatePassword2">Repeat Password</label>
<input type="password" name="customer[password]" id="CreatePassword2" class="{% if form.errors contains 'password' %} input--error{% endif %}">
<p class="text-center">
<input type="submit" value="{{ 'customer.register.submit' | t }}" class="btn">
</p>
{% endform %}
</div>
</div>
</div>
</div>
I thought that the part of
{{ form.errors | default_errors }}
Would return an error when the email is duplicate but it does nothing and the user just gets redirected to the main page. Any idea of how this can be accomplished? Thank you