[graph] More explicit error message if dot is not found (closes #253516)

1  import os.path as osp
2  import os
3  import sys
4  import tempfile
5  import codecs
6 +import errno
7 
8  def escape(value):
9      """Make <value> usable in a dot file."""
10      lines = [line.replace('"', '\\"') for line in value.split('\n')]
11      data = '\\l'.join(lines)

12          if target != 'dot':
13              if sys.platform == 'win32':
14                  use_shell = True
15              else:
16                  use_shell = False
17 -            if mapfile:
18 -                subprocess.call([self.renderer,  '-Tcmapx', '-o', mapfile, '-T', target, dot_sourcepath, '-o', outputfile],
19 -                                shell=use_shell)
20 -            else:
21 -                subprocess.call([self.renderer, '-T',  target,
22 -                                 dot_sourcepath, '-o',  outputfile],
23 -                                shell=use_shell)
24 +            try:
25 +                if mapfile:
26 +                    subprocess.call([self.renderer,  '-Tcmapx', '-o', mapfile, '-T', target, dot_sourcepath, '-o', outputfile],
27 +                                    shell=use_shell)
28 +                else:
29 +                    subprocess.call([self.renderer, '-T',  target,
30 +                                     dot_sourcepath, '-o',  outputfile],
31 +                                    shell=use_shell)
32 +            except OSError as e:
33 +                if e.errno == errno.ENOENT:
34 +                    e.strerror = 'File not found: {0}'.format(self.renderer)
35 +                    raise
36              os.unlink(dot_sourcepath)
37          return outputfile
38 
39      def emit(self, line):
40          """Adds <line> to final output."""