Description of problem:
Some functionality (visual two-pane diff of files in version control (hg)) of meld is unavailable if patch is not installed

Version-Release number of selected component (if applicable):
meld-1.3.2-1.fc14.noarch


Steps to Reproduce:
1. install meld, remove patch
2. create a mercurial working copy (repo), edit some files
3. cd to the directory and run the command 'meld .'
4. local modified files are displayed in meld window
5. double click on any locally modified text file (colored red)


Actual results:
See the terminal window, following error message is shown:

Traceback (most recent call last):
  File "/usr/share/meld/meld/task.py", line 130, in iteration
    ret = task()
  File "/usr/share/meld/meld/vcview.py", line 362, in run_diff_iter
    self.show_patch(prefix, patch)
  File "/usr/share/meld/meld/vcview.py", line 500, in show_patch
    if misc.write_pipe(patchcmd, patch) == 0:
  File "/usr/share/meld/meld/misc.py", line 242, in write_pipe
    proc = subprocess.Popen(command, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
  File "/usr/lib64/python2.7/subprocess.py", line 672, in __init__
    errread, errwrite)
  File "/usr/lib64/python2.7/subprocess.py", line 1201, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory


Expected results:
A visual two-pane diff of the file is shown in a new tab.
It can be easily checked by installing 'patch'

Additional info:
The 'command' variable in /usr/share/meld/meld/misc.py:242 in above stacktrace is:
['patch', '--strip=1', '--reverse', '--directory=/tmp/tmptnY5qf-meld']
which led me to discover that 'patch' is required but not installed.