matplotlib需要哪种latex字体？如何使其可用？

Question

下面运行this小示例的错误跟踪表明它找不到cmr12字体。我在我的系统（Ubuntu 16.10）中发现了以下文件：

./fonts/truetype/lyx/cmr12.ttf
./texlive/texmf-dist/fonts/source/public/cm/cmr12.mf
./texlive/texmf-dist/fonts/tfm/public/cm/cmr12.tfm
./texlive/texmf-dist/fonts/pk/ljfour/public/cm/dpi600/cmr12.pk
./texlive/texmf-dist/fonts/type1/public/amsfonts/cm/cmr12.pfb
./texlive/texmf-dist/fonts/type1/public/amsfonts/cm/cmr12.pfm
./texlive/texmf-dist/fonts/afm/public/amsfonts/cm/cmr12.afm

那么，matplotlib需要哪种字体以及如何使其可用？另外，为什么matplotlib要查找的字体文件没有扩展名？在

以下是线索：

^{pr2}$

更新以下是安装cm-super，清空缓存并使用--verbose-debug运行后的输出，如Gerard Rozsavolgyi的评论所示：

$HOME=/home/meir
matplotlib data path /usr/share/matplotlib/mpl-data

*****************************************************************
You have the following UNSUPPORTED LaTeX preamble customizations:

Please do not ask for support with these customizations active.
*****************************************************************

loaded rc file /etc/matplotlibrc
matplotlib version 1.5.1
verbose.level debug
interactive is False
platform is linux2
loaded modules: <dictionary-keyiterator object at 0x7fa923c0d7e0>
CACHEDIR=/home/meir/.cache/matplotlib
Using fontManager instance from /home/meir/.cache/matplotlib/fontList.cache
backend TkAgg version 8.6
findfont: Matching :family=sans-serif:style=normal:variant=normal:weight=400:stretch=normal:size=medium to Bitstream Vera Sans (u'/usr/share/fonts/truetype/ttf-bitstream-vera/Vera.ttf') with score of 0.000000
Assigning font /F1 = u'/usr/share/fonts/truetype/ttf-bitstream-vera/Vera.ttf'
findfont: Matching :family=sans-serif:style=normal:variant=normal:weight=400:stretch=normal:size=large to Bitstream Vera Sans (u'/usr/share/fonts/truetype/ttf-bitstream-vera/Vera.ttf') with score of 0.000000
Dvi: /home/meir/.cache/matplotlib/tex.cache/1d97300a39adbdb822e515e35e631e34.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
find_tex_file(phvr7t.tfm): [u'kpsewhich', u'phvr7t.tfm']
find_tex_file result: /usr/share/texlive/texmf-dist/fonts/tfm/adobe/helvetic/phvr7t.tfm
opening tfm file /usr/share/texlive/texmf-dist/fonts/tfm/adobe/helvetic/phvr7t.tfm
lh=18, bc=0, ec=170, nw=17, nh=16, nd=16
find_tex_file(phvr7t.vf): [u'kpsewhich', u'phvr7t.vf']
find_tex_file result: /usr/share/texlive/texmf-dist/fonts/vf/adobe/helvetic/phvr7t.vf
Dvi: /usr/share/texlive/texmf-dist/fonts/vf/adobe/helvetic/phvr7t.vf
find_tex_file(phvr8r.tfm): [u'kpsewhich', u'phvr8r.tfm']
find_tex_file result: /usr/share/texlive/texmf-dist/fonts/tfm/adobe/helvetic/phvr8r.tfm
opening tfm file /usr/share/texlive/texmf-dist/fonts/tfm/adobe/helvetic/phvr8r.tfm
lh=18, bc=1, ec=255, nw=30, nh=16, nd=16
find_tex_file(phvr8r.vf): [u'kpsewhich', u'phvr8r.vf']
find_tex_file result: 
Dvi._xxx: encountered special: Warning: missing glyph `Gamma'
Dvi._xxx: encountered special: Warning: missing glyph `Delta'
Dvi._xxx: encountered special: Warning: missing glyph `Theta'
Dvi._xxx: encountered special: Warning: missing glyph `Lambda'
Dvi._xxx: encountered special: Warning: missing glyph `Xi'
Dvi._xxx: encountered special: Warning: missing glyph `Pi'
Dvi._xxx: encountered special: Warning: missing glyph `Sigma'
Dvi._xxx: encountered special: Warning: missing glyph `Upsilon'
Dvi._xxx: encountered special: Warning: missing glyph `Phi'
Dvi._xxx: encountered special: Warning: missing glyph `Psi'
Dvi._xxx: encountered special: Warning: missing glyph `Omega'
Dvi._xxx: encountered special: Warning: missing glyph `dotlessj'
Dvi._xxx: encountered special: Warning: missing glyph `lslashslash'
Dvi: /home/meir/.cache/matplotlib/tex.cache/d0e4b65f3cbceaa40d39cd0b4aa94322.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
find_tex_file(cmr12.tfm): [u'kpsewhich', u'cmr12.tfm']
find_tex_file result: ./cmr12.tfm
opening tfm file ./cmr12.tfm
lh=18, bc=0, ec=127, nw=34, nh=16, nd=10
find_tex_file(cmr12.vf): [u'kpsewhich', u'cmr12.vf']
find_tex_file result: 
Dvi: /home/meir/.cache/matplotlib/tex.cache/1d97300a39adbdb822e515e35e631e34.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Dvi: /home/meir/.cache/matplotlib/tex.cache/04a76deccffda905e8691101fef1fc76.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Dvi: /home/meir/.cache/matplotlib/tex.cache/1d97300a39adbdb822e515e35e631e34.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Dvi: /home/meir/.cache/matplotlib/tex.cache/bbd64720c31d6f90a40311f23be42459.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Dvi: /home/meir/.cache/matplotlib/tex.cache/1d97300a39adbdb822e515e35e631e34.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Dvi: /home/meir/.cache/matplotlib/tex.cache/fe6359652f3a3d1ffea98277430a2e0d.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Dvi: /home/meir/.cache/matplotlib/tex.cache/1d97300a39adbdb822e515e35e631e34.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Dvi: /home/meir/.cache/matplotlib/tex.cache/4f1d4aac6b5a9606c9b7534411317104.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Dvi: /home/meir/.cache/matplotlib/tex.cache/1d97300a39adbdb822e515e35e631e34.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Dvi: /home/meir/.cache/matplotlib/tex.cache/75f66faa7396d6de47d7fef88d0cdf18.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Dvi: /home/meir/.cache/matplotlib/tex.cache/d0e4b65f3cbceaa40d39cd0b4aa94322.dvi
Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
Assigning font /F2 = 'cmr12'
find_tex_file(pdftex.map): [u'kpsewhich', u'pdftex.map']
find_tex_file result: /var/lib/texmf/fonts/map/pdftex/updmap/pdftex.map
Embedding font /usr/share/fonts/truetype/ttf-bitstream-vera/Vera.ttf
Writing TrueType font
Embedding font cmr12
Writing TrueType font
Traceback (most recent call last):
  File "temp.py", line 49, in <module>
    d['ModDate'] = datetime.datetime.today()
  File "/usr/lib/python2.7/dist-packages/matplotlib/backends/backend_pdf.py", line 2435, in __exit__
    self.close()
  File "/usr/lib/python2.7/dist-packages/matplotlib/backends/backend_pdf.py", line 2442, in close
    self._file.close()
  File "/usr/lib/python2.7/dist-packages/matplotlib/backends/backend_pdf.py", line 547, in close
    self.writeFonts()
  File "/usr/lib/python2.7/dist-packages/matplotlib/backends/backend_pdf.py", line 647, in writeFonts
    realpath, stat_key = get_realpath_and_stat(filename)
  File "/usr/lib/python2.7/dist-packages/matplotlib/cbook.py", line 1038, in __call__
    stat = os.stat(realpath)
OSError: [Errno 2] No such file or directory: '/home/meir/Dropbox/temp/cmr12'