Android Error: Apache HttpClient does not exist

Now it is mandatory for google to have in the code that update where the version is changed of targetSdkVersion to apply the latest APIs in the applications.

I changed the values from SdkVersion to 26 as recommended by google play.

    apply plugin: 'com.android.application'    
android {
    compileSdkVersion 26
    buildToolsVersion '26.0.2'

    defaultConfig {
        minSdkVersion 15
        targetSdkVersion 26
    }

But when performing the build, the application returns me the error about package org.apache.http can not be found along with other properties of the file as classes and variáveis .

Error:(19, 23) error: package org.apache.http does not exist
Error:(20, 23) error: package org.apache.http does not exist    
Error:(230, 13) error: cannot find symbol class HttpEntity
Error:(231, 29) error: cannot find symbol variable EntityUtils    

I'm forgetting to put some information in my code? For the only thing I changed was the number of SdkVersion . How can I resolve this problem?