Slightly improve output of dvi debug utilities, and tiny cleanups.

New output of `python -mmatplotlib.dviread /path/to/dvi` for
`$\frac{1}{2}$`:
```
=== new page === (w: 261235, h: 553676, d: 225994)
font: 'cmr7'    scale: 0.4375
x       y       glyph   chr     w       (glyphs)
1061683 1183756 49      1       261235
1061683 1667786 50      2       261235
x       y       w       h               (boxes)
1061683 1291058 26213 261235
```
old output:
```
=== new page ===
font b'cmr7' scaled 0.4375
1061683 1183756 49 1 261235
1061683 1667786 50 2 261235
1061683 1291058 BOX 26213 261235
```

Author: anntzer

lib/matplotlib/dviread.py

@@ -259,8 +259,8 @@ def _output(self):
         for elt in self.text + self.boxes:
             if isinstance(elt, Box):
                 x, y, h, w = elt
-                e = 0           # zero depth
-            else:               # glyph
+                e = 0  # zero depth
+            else:  # glyph
                 x, y, font, g, w = elt
                 h, e = font._height_depth_of(g)
             minx = min(minx, x)
@@ -1044,14 +1044,19 @@ def _fontfile(cls, suffix, texname):
     with Dvi(args.filename, args.dpi) as dvi:
         fontmap = PsfontsMap(find_tex_file('pdftex.map'))
         for page in dvi:
-            print('=== new page ===')
+            print(f"=== new page === "
+                  f"(w: {page.width}, h: {page.height}, d: {page.descent})")
             for font, group in itertools.groupby(
                     page.text, lambda text: text.font):
-                print('font', font.texname, 'scaled', font._scale / 2 ** 20)
+                print(f"font: {font.texname.decode('latin-1')!r}\t"
+                      f"scale: {font._scale / 2 ** 20}")
+                print("x", "y", "glyph", "chr", "w", "(glyphs)", sep="\t")
                 for text in group:
                     print(text.x, text.y, text.glyph,
                           chr(text.glyph) if chr(text.glyph).isprintable()
                           else ".",
-                          text.width)
-            for x, y, w, h in page.boxes:
-                print(x, y, 'BOX', w, h)
+                          text.width, sep="\t")
+            if page.boxes:
+                print("x", "y", "w", "h", "", "(boxes)", sep="\t")
+                for x, y, w, h in page.boxes:
+                    print(x, y, w, h, sep="\t")