Only externally define versions that are used multiple times

build.gradle

@@ -1,14 +1,8 @@
 import java.security.MessageDigest
 
 buildscript {
-    ext.gradle_version = "3.4.1"
     ext.kotlin_version = "1.3.31"
     ext.kovenant_version = "3.3.0"
-    ext.identicon_version = "v11"
-    ext.rss_parser_version = "2.0.4"
-    ext.google_services_version = "4.3.3"
-    ext.firebase_messaging_version = "18.0.0"
-    ext.opencsv_version = "4.6"
 
     repositories {
         mavenLocal()
@@ -16,10 +10,10 @@ buildscript {
         mavenCentral()
     }
     dependencies {
-        classpath "com.android.tools.build:gradle:$gradle_version"
+        classpath "com.android.tools.build:gradle:3.4.1"
         classpath files('libs/gradle-witness.jar')
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-        classpath "com.google.gms:google-services:$google_services_version"
+        classpath "com.google.gms:google-services:4.3.3"
     }
 }
 
@@ -91,7 +85,7 @@ dependencies {
     implementation 'androidx.lifecycle:lifecycle-extensions:2.0.0'
     implementation 'androidx.lifecycle:lifecycle-common-java8:2.0.0'
 
-    implementation ("com.google.firebase:firebase-messaging:$firebase_messaging_version") {
+    implementation ("com.google.firebase:firebase-messaging:18.0.0") {
         exclude group: 'com.google.firebase', module: 'firebase-core'
         exclude group: 'com.google.firebase', module: 'firebase-analytics'
         exclude group: 'com.google.firebase', module: 'firebase-measurement-connector'
@@ -187,12 +181,12 @@ dependencies {
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
     implementation "nl.komponents.kovenant:kovenant:$kovenant_version"
     implementation "nl.komponents.kovenant:kovenant-android:$kovenant_version"
-    implementation "com.github.lelloman:android-identicons:$identicon_version"
+    implementation "com.github.lelloman:android-identicons:v11"
-    implementation "com.prof.rssparser:rssparser:$rss_parser_version"
+    implementation "com.prof.rssparser:rssparser:2.0.4"
     implementation "com.jakewharton.rxbinding3:rxbinding:3.1.0"
     implementation "com.github.tbruyelle:rxpermissions:0.10.2"
     implementation "com.github.ybq:Android-SpinKit:1.4.0"
-    implementation "com.opencsv:opencsv:$opencsv_version"
+    implementation "com.opencsv:opencsv:4.6"
 }
 
 def canonicalVersionCode = 65