import fileinput

#prepare empty file to open in case of IOerror
open('dummy', 'w').close()

def hook_skip_IOerror(filename, mode):
        try:
            return open(filename, mode)
        except IOError:
            print("There was a problem with opening %s" % filename)
            return open('dummy', mode)          

def process(searchterm):
    for line in fileinput.input(openhook=hook_skip_IOerror):
        if line is not None:
           num_matches = line.count(searchterm)
           if num_matches:                     # a nonzero count means there was a match
               print "found '%s' %d times in %s on line %d." % (searchterm, num_matches,
                   fileinput.filename(), fileinput.filelineno())

process('=')