Ändern Sie die Standardnachricht des erforderlichen Feldeingangs Popover

//Just Use oninvalid & oninput Like Bellow
<input class="form-control" type="email"  required="" placeholder="username"
 oninvalid="this.setCustomValidity('Please Enter valid email')"
 oninput="setCustomValidity('')"></input>
Amin Arjmand