ERROR: matplotlib.tests.test_backend_pgf.test_pdflatex on Python 3.x

[mdboom]

I'm getting this on Python 3.x only.

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ERROR: matplotlib.tests.test_backend_pgf.test_pdflatex
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Traceback (most recent call last):
  File "/home/mdboom/python3/lib/python3.2/site-packages/nose/case.py", line 198, in runTest
    self.test(*self.arg)
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/testing/decorators.py", line 39, in failer
    result = f(*args, **kwargs)
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/tests/test_backend_pgf.py", line 30, in backend_switcher
    result = func(*args, **kwargs)
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/tests/test_backend_pgf.py", line 82, in test_pdflatex
    compare_figure('pgf_pdflatex.pdf')
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/tests/test_backend_pgf.py", line 40, in compare_figure
    plt.savefig(actual)
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/pyplot.py", line 475, in savefig
    return fig.savefig(*args, **kwargs)
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/figure.py", line 1229, in savefig
    self.canvas.print_figure(*args, **kwargs)
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/backend_bases.py", line 2089, in print_figure
    **kwargs)
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/backends/backend_pgf.py", line 694, in print_pdf
    self.print_pgf("figure.pgf")
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/backends/backend_pgf.py", line 674, in print_pgf
    renderer = RendererPgf(self.figure, fh)
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/backends/backend_pgf.py", line 358, in __init__
    self.latexManager = LatexManagerFactory.get_latex_manager()
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/backends/backend_pgf.py", line 205, in get_latex_manager
    new_inst = LatexManager()
  File "/home/mdboom/python3/lib/python3.2/site-packages/matplotlib/backends/backend_pgf.py", line 243, in __init__
    stdout, stderr = latex.communicate(self.latex_header + latex_end)
  File "/usr/lib64/python3.2/subprocess.py", line 819, in communicate
    return self._communicate(input)
  File "/usr/lib64/python3.2/subprocess.py", line 1425, in _communicate
    stdout, stderr = self._communicate_with_poll(input)
  File "/usr/lib64/python3.2/subprocess.py", line 1492, in _communicate_with_poll
    input_offset += os.write(fd, chunk)
TypeError: 'str' does not support the buffer interface

[pwuertz]

I have never worked with python3 before :/, but it looks like the py3 distinction between strings and bytes. Subprocess.communicate requires a byte buffer that must be explicitly encoded from a str.. (self.latex_header + latex_end).encode('utf-8')..

I'll try to setup a python 3 environment then ^^

[pwuertz]

Ok. Another problem. For me, in python3 this doesn't work anymore:

import codecs
import subprocess

proc = subprocess.Popen(["echo"], stdin=subprocess.PIPE,
                                  stdout=subprocess.PIPE,
                                  universal_newlines=True)
proc_stdin = codecs.getwriter("utf8")(proc.stdin)
proc_stdin.write("")
proc.communicate()

Apparently, the universal_newlines support is gone. It works if you omit this option. I don't know if this is a problem for windows or osx. For windows it's probably ok since I check for a latex prompt after newline.. and even with '\r\n' the newline is still the last character of a line. What about osx? Are they still using '\r' as a newline? I better find someone to test this :)

[pwuertz]

All right, I rewrote the part for the communication with the latex subprocess. Python3 seems to have trouble with subprocess+codecs+latex, so I'm using bytebuffers for reading the stdout now. Python2 tests pass, running a python3 example works, but I can't run the test suite with py3 yet (#745).