Use \N{MICRO SIGN} instead of \N{GREEK SMALL LETTER MU} in EngFormatter.

anntzer · anntzer · commit 54037c189bcb · 2018-10-10T17:00:43.000+02:00
This is semantically more correct, and, more importantly, is covered by
the pdf 14 core fonts: after

```
from matplotlib.ticker import EngFormatter
from pylab import *

rcParams["pdf.use14corefonts"] = True
fig, ax = plt.subplots()
ax.semilogx([1e-6, 1e-5], [0, 1])
ax.xaxis.set_major_formatter(EngFormatter(unit="s"))
savefig("/tmp/test.pdf")
```

we previously got a pdf where the µ signs were replaced by question
marks (actually this happens at the encoding to cp1252 stage), whereas
with the fix, the µ signs appear correctly.
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -1187,7 +1187,7 @@ class EngFormatter(Formatter):
         -15: "f",
         -12: "p",
          -9: "n",
-         -6: "\N{GREEK SMALL LETTER MU}",
+         -6: "\N{MICRO SIGN}",
          -3: "m",
           0: "",
           3: "k",
@@ -1251,7 +1251,7 @@ def format_eng(self, num):
         '1.0 M'
 
         >>> format_eng("-1e-6") # for self.places = 2
-        '-1.00 \N{GREEK SMALL LETTER MU}'
+        '-1.00 \N{MICRO SIGN}'
         """
         sign = 1
         fmt = "g" if self.places is None else ".{:d}f".format(self.places)
