fix indentation, use python2 - not compatible with python3

[gefa]

This solves the error(s) when uploading code to sky (telos b) device:

msp430-objcopy throughput-test.sky -O ihex throughput-test.ihex
make IHEXFILE=throughput-test.ihex sky-reset sky-upload
make[1]: Entering directory '/home/gefa/workspace/contiki-forked/examples/sky'
make -k -j 20 sky-reset-sequence
make[2]: Entering directory '/home/gefa/workspace/contiki-forked/examples/sky'
../../tools/sky/msp430-bsl-linux --telosb -c /dev/ttyUSB1 -r
 File "../../tools/sky/msp430-bsl-linux", line 272
   self.swapRSTTEST = 0
                      ^
TabError: inconsistent use of tabs and spaces in indentation
make[2]: *** [../../platform/sky/Makefile.common:155: sky-r._dev_ttyUSB1] Error 1
make[2]: Target 'sky-reset-sequence' not remade because of errors.
make[2]: Leaving directory '/home/gefa/workspace/contiki-forked/examples/sky'
make[1]: *** [../../platform/sky/Makefile.common:141: sky-reset] Error 2
make[1]: Leaving directory '/home/gefa/workspace/contiki-forked/examples/sky'
make: *** [../../platform/sky/Makefile.common:119: throughput-test.upload] Error 2
rm throughput-test.ihex