[opt-viewer] Mention Pygments in the description

llvm-svn: 286535

Author: anemet

llvm/utils/opt-viewer/opt-viewer.py

@@ -5,7 +5,7 @@
 desc = '''Generate HTML output to visualize optimization records from the YAML files
 generated with -fsave-optimization-record and -fdiagnostics-show-hotness.
 
-The tools requires PyYAML to be installed.'''
+The tools requires PyYAML and Pygments Python packages.'''
 
 import yaml
 import argparse