I want to put an image inside a button in a tree view of a custom module in odoo 9.

I have 2 buttons in my\_module.xml:

```
<?xml version="1.0"?>
<openerp>
    <data>
        <record id="view_my_module_tree" model="ir.ui.view">
            <field name="name">my.module.tree</field>
            <field name="model">my.module</field>
            <field name="type">tree</field>
            <field name="arch" type="xml">
                <tree string="my_module_tree" create="false" delete="false">
                    <button name="button_form" icon="cat" type="object"/>
                    <button name="button_form" icon="dog" type="object"/>                   
                </tree>
            </field>
        </record>  
    </data>
</openerp>

```

That works if the icons 'cat.png' and dog.png' are inside 'addons/web/static/src/img/icons/'. But I want to put this icons in my custom module.

I have created the 'my\_module/static/src/img/icons/' hierarchy and put both images inside, but none of them appear in the buttons.

What I am doing wrong? 
Do I need to put something in openerp.py file?

**Edit:** I have tried this 

```
<button name="button_form" type="object" icon="/my_module/static/src/img/icons/cat.png"/> 

```

But it doesn't work. If I see in the browser DevTools, I can check in the html code that: 

```
<img src="http://localhost:8069/web/static/src/img/icons//my_module/static/src/img/icons/cat.png.png">

```

That has sense with the source code of the WidgetButton (it appends to '/web/static/src/img/icons/' your image path, and then adds '.png' at the end But of course, that doesn't solve the problem.