Fix check for dmenu (open file mode, dependency on which).

See <https://github.com/proxypoke/quickswitch-for-i3/pull/24>.

--- quickswitch-i3-2.2/quickswitch.py	2016-09-18 19:59:10.257765542 +0200
+++ quickswitch-i3-2.2/quickswitch.py	2016-09-21 10:43:01.277577819 +0200
@@ -24,9 +24,10 @@
 
 import argparse
 import subprocess
-import os
 import re
 
+from distutils.spawn import find_executable
+
 try:
     import i3
 except ImportError:
@@ -37,11 +38,8 @@
 
 def check_dmenu():
     '''Check if dmenu is available.'''
-    devnull = open(os.devnull)
-    retcode = subprocess.call(["which", "dmenu"],
-                              stdout=devnull,
-                              stderr=devnull)
-    return True if retcode == 0 else False
+    executable = find_executable("dmenu")
+    return executable != None
 
 
 def dmenu(options, dmenu):
ue='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
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<tr><td><span title='2020-08-27 18:18:55 +0300'>2020-08-27</span></td><td><a href='/guix/commit/gnu/packages/patches/vcflib-use-shared-libraries.patch?id=6d8dd5bad773a9bc4eaf0b3c13dd9c373c3546c3'>gnu: vcflib: Use shared libraries.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/bioinformatics.scm (vcflib)[source]: Add patch. Add
snippet to adjust files for new locations.
[inputs]: Add fastahack, smithwaterman, tabixpp, xz.
[native-inputs]: Add pkg-config. Remove the package-source of fastahack,
fsom, smithwaterman, tabixpp.
[arguments]: Remove make-flags. Add custom phase to add the output lib
directory to the rpath. Adjust custom 'unpack-submodule-sources for the
change in native-inputs. Adjust custom 'install phase to also install
libraries and headers.
* gnu/packages/patches/vcflib-use-shared-libraries.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.
</span></span></td><td>Efraim Flashner</td></tr>