Hello, I want to inherit base common button template in custom module. I work with odoo V10
A try this : 

<?xml version="1.0" encoding="UTF-8"?>
<templates id="web.template" xml:space="preserve">
		<xpath expr="//button" position="relace">
            	<button type="button" t-attf-class="btn btn-sm #{widget.node.attrs.class or ''}"
		        t-att-style="widget.node.attrs.style"
		        t-att-tabindex="widget.node.attrs.tabindex"
		        t-att-autofocus="widget.node.attrs.autofocus"
		        t-att-accesskey="widget.node.attrs.accesskey">
		        <t t-if="widget.node.attrs.icon">
		            <img t-if="!widget.fa_icon" t-att-src="widget.node.attrs.icon" style="color:green"/>
		            <div t-if="widget.fa_icon" t-attf-class="fa fa-fw #{widget.node.attrs.icon} o_button_icon" style="color:green"/>
		        </t>
		        <span t-if="widget.string"><t t-esc="widget.string"/></span>
		    </button>
		</xpath>    
    
</templates>

and this : 

<?xml version="1.0" encoding="UTF-8"?>
<templates id="web.template" xml:space="preserve">	
	<t t-name="CapWidgetButton" t-extend="WidgetButton">
        <t t-jquery='button' t-operation='replace'>
        	<button type="button" t-attf-class="btn btn-sm #{widget.node.attrs.class or ''}"
		        t-att-style="widget.node.attrs.style"
		        t-att-tabindex="widget.node.attrs.tabindex"
		        t-att-autofocus="widget.node.attrs.autofocus"
		        t-att-accesskey="widget.node.attrs.accesskey">
		        <t t-if="widget.node.attrs.icon">
		            <img t-if="!widget.fa_icon" t-att-src="widget.node.attrs.icon" style="color:green"/>
		            <div t-if="widget.fa_icon" t-attf-class="fa fa-fw #{widget.node.attrs.icon} o_button_icon" style="color:green"/>
		        </t>
		        <span t-if="widget.string"><t t-esc="widget.string"/></span>
		    </button>
        </t>
	</t>
</templates>

But i doesn't work. Have you any idea ?