Move checkdep_ps_distiller to the rc validators.

lib/matplotlib/__init__.py

@@ -440,6 +440,7 @@ def checkdep_inkscape():
 checkdep_inkscape.version = None
 
 
+@cbook.deprecated("2.2")
 def checkdep_ps_distiller(s):
     if not s:
         return False
@@ -449,7 +450,7 @@ def checkdep_ps_distiller(s):
         return False
     if s == "xpdf" and not get_executable_info("pdftops"):
         warnings.warn(
-            "setting matplotlibrc ps.usedistiller to 'xpdf' requires xpdf.")
+            "Setting matplotlibrc ps.usedistiller to 'xpdf' requires xpdf.")
         return False
     return s
 
@@ -1066,9 +1067,6 @@ def rc_params_from_file(fname, fail_on_error=False, use_default_template=True):
                             six.iteritems(defaultParams)
                             if key not in _all_deprecated])
 
-rcParams['ps.usedistiller'] = checkdep_ps_distiller(
-                      rcParams['ps.usedistiller'])
-
 rcParams['text.usetex'] = checkdep_usetex(rcParams['text.usetex'])
 
 if rcParams['axes.formatter.use_locale']:

lib/matplotlib/rcsetup.py

@@ -25,6 +25,7 @@
 import warnings
 import re
 
+import matplotlib as mpl
 from matplotlib.cbook import mplDeprecation, deprecated, ls_mapper
 from matplotlib.fontconfig_pattern import parse_fontconfig_pattern
 from matplotlib.colors import is_color_like
@@ -505,7 +506,12 @@ def validate_ps_distiller(s):
     elif s in ('false', False):
         return False
     elif s in ('ghostscript', 'xpdf'):
-        return s
+        if not mpl.get_executable_info("gs"):
+            warnings.warn("Setting ps.usedistiller requires ghostscript.")
+            return False
+        if s == "xpdf" and not mpl.get_executable_info("pdftops"):
+            warnings.warn("Setting ps.usedistiller to 'xpdf' requires xpdf.")
+            return False
     else:
         raise ValueError('matplotlibrc ps.usedistiller must either be none, '
                          'ghostscript or xpdf')