usertools: check for lspci dependency

On some distributions (such as CentOS 7) lspci may not be installed
by default, causing exceptions which are difficult to interpret.

Fix devbind script to check if lspci is installed at script startup.

Cc: stable@dpdk.org

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Reviewed-by: Rami Rosen <roszenrami@gmail.com>

usertools/dpdk-devbind.py

@@ -655,6 +655,13 @@ def do_arg_actions():
 
 def main():
     '''program main function'''
+    # check if lspci is installed, suppress any output
+    with open(os.devnull, 'w') as devnull:
+        ret = subprocess.call(['which', 'lspci'],
+                              stdout=devnull, stderr=devnull)
+        if ret != 0:
+            print("'lspci' not found - please install 'pciutils'")
+            sys.exit(1)
     parse_args()
     check_modules()
     clear_data()