For me say that is missing extension.json on wikimedia 1.28.
Resolved as follow:
My file extension.json content (most of them fields could be removed.... I just copy and adapt it from another extension):
{
"name": "LastUserLogin",
"version": "1.3",
"author": [
"Justin G. Cramer", "Danila Ulyanov", "Thomas Klein", "Felipe Schenone"
],
"url": "https://www.mediawiki.org/wiki/Extension:LastUserLogin",
"descriptionmsg": "lastuserlogin-desc",
"license-name": "GPL-2.0+",
"type": "specialpage",
"AvailableRights": [
"lastuserlogin"
],
"LogTypes": [
"lastuserlogin"
],
"LogNames": {
"lastuserlogin": "lastuserlogin-logpage"
},
"LogHeaders": {
"lastuserlogin": "lastuserlogin-logpagetext"
},
"LogActions": {
"lastuserlogin/lastuserlogin": "lastuserlogin-success-log"
},
"MessagesDirs": {
"LastUserLogin": [
"i18n"
]
},
"ExtensionMessagesFiles": {
"LastUserLoginAlias": "LastUserLogin.alias.php"
},
"AutoloadClasses": {
"LastUserLogin": "LastUserLogin.php"
},
"config": {
},
"manifest_version": 1
}