title: Mysterious UnicodeDecodeError in python3 while building Docker container
body: <p>I am creating a python 3 application. 
  <a href="https://github.com/Omrigan/TED-analysis" rel="noreferrer">https://github.com/Omrigan/TED-analysis</a></p>
  
  <p>To deploy I want to use Docker with Dockerfile located in root of my Github repo (you may check it). So, when I do "docker build ." I get an error on this line: </p>
  
  <pre><code>RUN pip3 install --upgrade  -r /root/ted_talks/requirements.txt
  </code></pre>
  
  <p>Log from console: </p>
  
  <pre><code>  Collecting httpretty==0.8.10 (from smart-open&gt;=1.2.1-&gt;gensim-&gt;-r /root/ted_talks/requirements.txt (line 4))
    Downloading httpretty-0.8.10.tar.gz (41kB)
      Complete output from command python setup.py egg_info:
      Traceback (most recent call last):
        File "&lt;string&gt;", line 1, in &lt;module&gt;
        File "/tmp/pip-build-em459e9u/httpretty/setup.py", line 86, in &lt;module&gt;
          version=read_version(),
        File "/tmp/pip-build-em459e9u/httpretty/setup.py", line 46, in read_version
          finder.visit(ast.parse(local_file('httpretty', '__init__.py')))
        File "/tmp/pip-build-em459e9u/httpretty/setup.py", line 78, in &lt;lambda&gt;
          open(os.path.join(os.path.dirname(__file__), *f)).read()
        File "/usr/lib/python3.4/encodings/ascii.py", line 26, in decode
          return codecs.ascii_decode(input, self.errors)[0]
      UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 133: ordinal not in range(128)
  </code></pre>
  
  <p>So, what should I do?</p>