Error type for optional executable dependencies

Author: alexrudy

lib/matplotlib/__init__.py

@@ -282,6 +282,9 @@ def wrapper():
 
 _ExecInfo = namedtuple("_ExecInfo", "executable version")
 
+class ExecutableUnavailableError(FileNotFoundError):
+    """Error raised when an executable that Matplotlib optionally depends on can't be found."""
+    pass
 
 @functools.lru_cache()
 def _get_executable_info(name):
@@ -307,7 +310,7 @@ def _get_executable_info(name):
 
     Raises
     ------
-    FileNotFoundError
+    ExecutableUnavailableError
         If the executable is not found or older than the oldest version
         supported by Matplotlib.
     ValueError
@@ -319,25 +322,27 @@ def impl(args, regex, min_ver=None, ignore_exit_code=False):
         # Search for a regex match in the output; if the match succeeds, the
         # first group of the match is the version.
         # Return an _ExecInfo if the executable exists, and has a version of
-        # at least min_ver (if set); else, raise FileNotFoundError.
+        # at least min_ver (if set); else, raise ExecutableUnavailableError.
         try:
             output = subprocess.check_output(
                 args, stderr=subprocess.STDOUT, universal_newlines=True)
         except subprocess.CalledProcessError as _cpe:
             if ignore_exit_code:
                 output = _cpe.output
             else:
-                raise _cpe
+                raise ExecutableUnavailableError(str(_cpe)) from _cpe
+        except FileNotFoundError as _fnf:
+            raise ExecutableUnavailableError(str(_fnf)) from _fnf
         match = re.search(regex, output)
         if match:
             version = LooseVersion(match.group(1))
             if min_ver is not None and version < min_ver:
-                raise FileNotFoundError(
+                raise ExecutableUnavailableError(
                     f"You have {args[0]} version {version} but the minimum "
                     f"version supported by Matplotlib is {min_ver}.")
             return _ExecInfo(args[0], version)
         else:
-            raise FileNotFoundError(
+            raise ExecutableUnavailableError(
                 f"Failed to determine the version of {args[0]} from "
                 f"{' '.join(args)}, which output {output}")
 
@@ -350,9 +355,9 @@ def impl(args, regex, min_ver=None, ignore_exit_code=False):
         for e in execs:
             try:
                 return impl([e, "--version"], "(.*)", "9")
-            except FileNotFoundError:
+            except ExecutableUnavailableError:
                 pass
-        raise FileNotFoundError("Failed to find a Ghostscript installation")
+        raise ExecutableUnavailableError("Failed to find a Ghostscript installation")
     elif name == "inkscape":
         return impl(["inkscape", "-V"], "^Inkscape ([^ ]*)")
     elif name == "magick":
@@ -380,7 +385,7 @@ def impl(args, regex, min_ver=None, ignore_exit_code=False):
         else:
             path = "convert"
         if path is None:
-            raise FileNotFoundError(
+            raise ExecutableUnavailableError(
                 "Failed to find an ImageMagick installation")
         return impl([path, "--version"], r"^Version: ImageMagick (\S*)")
     elif name == "pdftops":
@@ -389,7 +394,7 @@ def impl(args, regex, min_ver=None, ignore_exit_code=False):
         if info and not ("3.0" <= info.version
                          # poppler version numbers.
                          or "0.9" <= info.version <= "1.0"):
-            raise FileNotFoundError(
+            raise ExecutableUnavailableError(
                 f"You have pdftops version {info.version} but the minimum "
                 f"version supported by Matplotlib is 3.0.")
         return info
@@ -478,14 +483,14 @@ def checkdep_ps_distiller(s):
         return False
     try:
         _get_executable_info("gs")
-    except FileNotFoundError:
+    except ExecutableUnavailableError:
         _log.warning(
             "Setting rcParams['ps.usedistiller'] requires ghostscript.")
         return False
     if s == "xpdf":
         try:
             _get_executable_info("pdftops")
-        except FileNotFoundError:
+        except ExecutableUnavailableError:
             _log.warning(
                 "Setting rcParams['ps.usedistiller'] to 'xpdf' requires xpdf.")
             return False
@@ -500,12 +505,12 @@ def checkdep_usetex(s):
         return False
     try:
         _get_executable_info("dvipng")
-    except FileNotFoundError:
+    except ExecutableUnavailableError:
         _log.warning("usetex mode requires dvipng.")
         return False
     try:
         _get_executable_info("gs")
-    except FileNotFoundError:
+    except ExecutableUnavailableError:
         _log.warning("usetex mode requires ghostscript.")
         return False
     return True

lib/matplotlib/animation.py

@@ -725,7 +725,7 @@ def bin_path(cls):
     def isAvailable(cls):
         try:
             return super().isAvailable()
-        except FileNotFoundError:  # May be raised by get_executable_info.
+        except mpl.ExecutableUnavailableError:  # May be raised by get_executable_info.
             return False
 
 

lib/matplotlib/backends/backend_pgf.py

@@ -157,7 +157,7 @@ def cairo_convert(pdffile, pngfile, dpi):
         return cairo_convert
     try:
         gs_info = mpl._get_executable_info("gs")
-    except FileNotFoundError:
+    except mpl.ExecutableUnavailableError:
         pass
     else:
         def gs_convert(pdffile, pngfile, dpi):

lib/matplotlib/rcsetup.py

@@ -483,14 +483,14 @@ def validate_ps_distiller(s):
     elif s in ('ghostscript', 'xpdf'):
         try:
             mpl._get_executable_info("gs")
-        except FileNotFoundError:
+        except mpl.ExecutableUnavailableError:
             _log.warning("Setting rcParams['ps.usedistiller'] requires "
                          "ghostscript.")
             return None
         if s == "xpdf":
             try:
                 mpl._get_executable_info("pdftops")
-            except FileNotFoundError:
+            except mpl.ExecutableUnavailableError:
                 _log.warning("Setting rcParams['ps.usedistiller'] to 'xpdf' "
                              "requires xpdf.")
                 return None

lib/matplotlib/testing/compare.py

@@ -220,13 +220,13 @@ def __call__(self, orig, dest):
 def _update_converter():
     try:
         mpl._get_executable_info("gs")
-    except FileNotFoundError:
+    except mpl.ExecutableUnavailableError:
         pass
     else:
         converter['pdf'] = converter['eps'] = _GSConverter()
     try:
         mpl._get_executable_info("inkscape")
-    except FileNotFoundError:
+    except mpl.ExecutableUnavailableError:
         pass
     else:
         converter['svg'] = _SVGConverter()