vndk-def: Use EnvironmentError in Python 2

This commit uses `EnvironmentError` as a replacement for
`FileNotFoundError`, which was introduced in Python 3.  Before this
commit, `OSError` was chosen.  However, some Python API raises
`IOError` instead.

Bug: 113636759
Test: ./tests/run.py
Change-Id: I4a1cbceb3404dec243a60271a6fdb30703bc1060
1 file changed