Error:Execution failed for task ':app:validateExternalOverrideSigning'
<p>I am using caldroid library for calendar activity and It works fine.</p>

<p>But I needed to change it's style.</p>

<p>So I added caldroid library(directory) under the application like this.</p>

<p><img src="https://i.stack.imgur.com/xGS5A.png" alt="enter image description here"></p>

<p>and I changed my dependencies </p>

<blockquote>
  <p>dependencies {
     ...
      compile 'com.roomorama:caldroid:2.3.1'
     ...
  }</p>
</blockquote>

<p>to </p>

<blockquote>
  <p>dependencies {
     ...
      compile project(':libraries:caldroid')
     ...
  }</p>
</blockquote>

<p>Then, It works fine under the debug mode.</p>

<p>But I can't generate signed APK because of this message. </p>

<blockquote>
  <p>Error:Execution failed for task ':app:validateExternalOverrideSigning'.
  Keystore file /Users/xxxxxxx.android.keystore not found for signing config 'externalOverride'.</p>
</blockquote>

<p>Is there any solution about this error?</p>