最近学习python，遇到一个程序，运行出错，不知为什么。

程序如下：

#!/usr/bin/env python

'makeTextFile.py -- create text file'

import os
ls = os.linesep

# get filename
while True:

if os.path.exists(fname):
   print "ERROR: '%s' already exists" % fname
else:
   break

# get file content (text) lines
all = []
print "\nEnter lines ('.' by itself to quit).\n"

# loop until user terminates input
while True:
   entry = raw_input('> ')
   if entry == '.':
      break
   else:
      all.append(entry)

# write lines to file with proper line-ending
fobj = open(fname, 'w')
fobj.writelines(['%s%s' % (x, ls) for x in all])
fobj.close()
print 'DONE!'
 

运行出错如下：

  File "./makeTextFile.py", line 11
    if os.path.exists(fname):
     ^
IndentationError: expected an indented block