Little code and dependencies improvement in configure.sh

 The package 'build-essential' depends on the package 'gcc' and 'g++'.
Merge pull request #1114 from abderraouf-adjal/patch-3

Little code and dependencies improvement in configure.sh
C0103 fixes for local variables
bug fixes

- syntax error in ws.py 309 fixed
- syntax error in dht.py 353 fixed
- using exc variable for all exceptions
- using dict literal in openbazaar_demon.py 207
- replaced verification-var where it was unnecessary
fixed undefined variable bugs in dht.py