On Linux Mint 17.1 x86_64, Cordova v4.3.0 gives this error:
$ cordova run android
Running command: /home/naman/test/platforms/android/cordova/run
WARNING :
For others having this problem, assuming you have already checked and fixed any environment variables using @Naman Dixit's answer, you may also have to remove and add your platforms:
cmd: cordova platform rm [platform(s) of interest]
delete everything in the [yourproject]/platforms folder. Then:
cmd: cordova platform add [platform(s) of interest]
that was the final step I needed to get everything to work