The --packages option jars are getting added to the classpath with the scheme as "file:///", in Unix it doesn't have problem with this since the scheme contains the Unix Path separator which separates the jar name with location in the classpath. In Windows, the jar file is not getting resolved from the classpath because of the scheme.

Windows : file:///C:/Users/<user>/.ivy2/jars/<jar-name>.jar
Unix : file:///home/<user>/.ivy2/jars/<jar-name>.jar

With this PR, we are avoiding the 'file://' scheme to get added to the packages jar files.

I have verified manually in Windows and Unix environments, with the change it adds the jar to classpath like below,

Windows : C:\Users\<user>\.ivy2\jars\<jar-name>.jar
Unix : /home/<user>/.ivy2/jars/<jar-name>.jar

Author: Devaraj K <devaraj@apache.org>

Closes #18708 from devaraj-kavali/SPARK-21339.