Made modification of sys.path dependant on pyqtgraph import error

src/binwalk/__init__.py

@@ -3,7 +3,11 @@ __all__ = ['Modules', 'ModuleException']
 import sys
 import binwalk.core.common
 
-# This allows importing of the built-in pyqtgraph
-sys.path.append(binwalk.core.common.get_libs_path())
+# This allows importing of the built-in pyqtgraph if it
+# is not available on the system at run time.
+try:
+    import pyqtgraph
+except ImportError:
+    sys.path.append(binwalk.core.common.get_libs_path())
 
 from binwalk.core.module import Modules, ModuleException