title: Create conda environment: "Found conflicts!" when solving environment and "Finding shortest conflict path" running forever
body: <p>I was provided with an <code>environment.ubuntu.yml</code> file to be able to create a conda environment. However, running <code>conda create env --file environment.ubuntu.yml</code> I get the following output:</p>
  
  <pre><code>conda env create --file environment.ubuntu.yml
  Collecting package metadata (repodata.json): done
  Solving environment: - 
  Found conflicts! Looking for incompatible packages.
  This can take several minutes.  Press CTRL-C to abort.
  Examining fontconfig:   5%|▉                 | 10/202 [00:00&lt;00:00, 5393.91it/ ]
  Comparing specs that have this dependency:   0%|         | 0/12 [00:00&lt;?, ?it/s]
  Finding shortest confli|  path for fontconfig==2.13.1=he4413a7_1000:  12%|▏| 1/8
  Finding shortest conflict path for fontconfig==2.13.1=he4413a7_1000:  25%|▎| 2/8
  Finding shortest conflict pa/  for fontconfig[version='&gt;=2.13.0,&lt;3.0a0']:  25%|
  Finding shortest conflict path for fontconfig[version='&gt;=2.13.0,&lt;3.0a0']:  38%|
  Finding shortest conf- ct path for fontconfig[version='&gt;=2.11.1']:  38%|▍| 3/8 [
  Finding shortest conflict path for fontconfig[version='&gt;=2.11.1']:  50%|▌| 4/8 [
  Finding shortest conflict pa|  for fontconfig[version='&gt;=2.12.4,&lt;3.0a0']:  50%|
  ...
  </code></pre>
  
  <p>The <code>Finding shortest conflict path</code> goes on for a long time - apparently it is trying to resolve some dependency issues. Running for 2 hours it is not clear if it will ever stop.</p>
  
  <p>My question is: what is happening here and can I somehow manually speed up this process, e.g. by removing unnecessary dependencies? Since I did not create the environment I don't know which are actually necessary.</p>
  
  <p>The reason why I'm curious is because it is checking conflict paths like <code>fontconfig[version='&gt;=2.12.6,&lt;3.0a0']</code> when the one in <code>dependencies</code> is <code>2.13.1</code> and I have installed it through <code>2.13.1</code></p>
  
  <p>Please find below the .yml file for reference.</p>
  
  <pre><code>name: cea
  channels:
    - https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free
    - dlr-sc
    - https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/main
    - conda-forge
    - conda-forge/label/gcc7
    - defaults
  dependencies:
    - attrs=19.1.0=py_0
    - backports=1.0=py_2
    - backports.functools_lru_cache=1.5=py_1
    - backports_abc=0.5=py_1
    - boost-cpp=1.68.0=h11c811c_1000
    - bzip2=1.0.6=h14c3975_1002
    - ca-certificates=2019.3.9=hecc5488_0
    - cairo=1.14.12=h80bd089_1005
    - certifi=2019.3.9=py27_0
    - click=7.0=py_0
    - click-plugins=1.0.4=py_0
    - cligj=0.5.0=py_0
    - curl=7.64.1=hf8cf82a_0
    - cycler=0.10.0=py_1
    - descartes=1.1.0=py_2
    - enum34=1.1.6=py27_1001
    - expat=2.2.5=hf484d3e_1002
    - fiona=1.8.6=py27hf242f0b_2
    - fontconfig=2.13.1=he4413a7_1000
    - freetype=2.10.0=he983fc9_0
    - freexl=1.0.5=h14c3975_1002
    - functools32=3.2.3.2=py_3
    - futures=3.2.0=py27_1000
    - gdal=2.4.1=py27h5f563d9_8
    - geopandas=0.4.1=py_1
    - geos=3.7.1=hf484d3e_1000
    - geotiff=1.4.3=h1105359_1000
    - gettext=0.19.8.1=hc5be6a0_1002
    - giflib=5.1.7=h516909a_1
    - glib=2.56.2=had28632_1001
    - hdf4=4.2.13=h9a582f1_1002
    - hdf5=1.10.4=nompi_h3c11f04_1106
    - icu=58.2=hf484d3e_1000
    - jpeg=9c=h14c3975_1001
    - json-c=0.13.1=h14c3975_1001
    - kealib=1.4.10=h1978553_1003
    - kiwisolver=1.0.1=py27h6bb024c_1002
    - krb5=1.16.3=h05b26f9_1001
    - libblas=3.8.0=4_openblas
    - libcblas=3.8.0=4_openblas
    - libcurl=7.64.1=hda55be3_0
    - libdap4=3.19.1=hd48c02d_1000
    - libedit=3.1.20170329=hf8c457e_1001
    - libffi=3.2.1=he1b5a44_1006
    - libgdal=2.4.1=heae24aa_8
    - libiconv=1.15=h516909a_1005
    - libkml=1.3.0=h328b03d_1009
    - liblapack=3.8.0=4_openblas
    - libnetcdf=4.6.2=hbdf4f91_1001
    - libpng=1.6.36=h84994c4_1000
    - libpq=11.2=h4770945_0
    - libspatialindex=1.9.0=he1b5a44_0
    - libspatialite=4.3.0a=hb5ec416_1026
    - libssh2=1.8.2=h22169c7_2
    - libtiff=4.0.10=h648cc4a_1001
    - libuuid=2.32.1=h14c3975_1000
    - libxcb=1.13=h14c3975_1002
    - libxml2=2.9.8=h143f9aa_1005
    - mapclassify=1.0.1=py27_1
    - matplotlib=2.2.3=py27h8a2030e_1
    - matplotlib-base=2.2.3=py27h60b886d_1
    - munch=2.3.2=py_0
    - ncurses=6.1=hf484d3e_1002
    - numpy=1.16.2=py27h8b7e671_1
    - openblas=0.3.5=h9ac9557_1001
    - openjpeg=2.3.0=hf38bd82_1003
    - openssl=1.1.1b=h14c3975_1
    - pandas=0.24.2=py27hf484d3e_0
    - pip=19.0.3=py27_0
    - pixman=0.34.0=h14c3975_1003
    - poppler=0.67.0=h2fc8fa2_1002
    - poppler-data=0.4.9=1
    - postgresql=11.2=h61314c7_0
    - proj4=5.2.0=h14c3975_1001
    - pthread-stubs=0.4=h14c3975_1001
    - pyparsing=2.3.1=py_0
    - pyproj=1.9.6=py27hc0953d3_1000
    - pyqt=5.6.0=py27h13b7fb3_1008
    - python=2.7.15=h721da81_1008
    - python-dateutil=2.8.0=py_0
    - pytz=2018.9=py_0
    - readline=7.0=hf8c457e_1001
    - rtree=0.8.3=py27h666c49c_1002
    - scipy=1.2.1=py27h09a28d5_1
    - setuptools=40.8.0=py27_0
    - shapely=1.6.4=py27h2afed24_1003
    - singledispatch=3.4.0.3=py27_1000
    - sip=4.18.1=py27hf484d3e_1000
    - six=1.12.0=py27_1000
    - sqlite=3.26.0=h67949de_1001
    - subprocess32=3.5.3=py27h14c3975_0
    - tbb=2019.5=hc9558a2_0
    - tk=8.6.9=h84994c4_1001
    - tornado=5.1.1=py27h14c3975_1000
    - tzcode=2018g=h14c3975_1001
    - wheel=0.33.1=py27_0
    - xerces-c=3.2.2=hac72e42_1001
    - xorg-kbproto=1.0.7=h14c3975_1002
    - xorg-libice=1.0.9=h516909a_1004
    - xorg-libsm=1.2.3=h84519dc_1000
    - xorg-libx11=1.6.7=h14c3975_1000
    - xorg-libxau=1.0.9=h14c3975_0
    - xorg-libxdmcp=1.1.3=h516909a_0
    - xorg-libxext=1.3.4=h516909a_0
    - xorg-libxrender=0.9.10=h516909a_1002
    - xorg-renderproto=0.11.1=h14c3975_1002
    - xorg-xextproto=7.3.0=h14c3975_1002
    - xorg-xproto=7.0.31=h14c3975_1007
    - xz=5.2.4=h14c3975_1001
    - zlib=1.2.11=h14c3975_1004
    - freeimageplus=3.18.0=hf484d3e_2
    - gl2ps=1.3.8=h14c3975_4
    - oce=0.17.2=h6bb024c_10
    - pythonocc-core=0.17=py27_1
    - mkl=2017.0.3=0
    - mkl-service=1.1.2=py27_3
    - dbus=1.13.2=h714fa37_1
    - gst-plugins-base=1.14.0=hbbd80ab_1
    - gstreamer=1.14.0=hb453b48_1
    - libgcc-ng=8.2.0=hdf63c60_1
    - libgfortran-ng=7.3.0=hdf63c60_0
    - libstdcxx-ng=8.2.0=hdf63c60_1
    - pcre=8.43=he6710b0_0
    - qt=5.6.3=h8bf5577_3
    - pip:
      - alabaster==0.7.12
      - babel==2.6.0
      - backports.shutil-get-terminal-size==1.0.0
      - bleach==3.1.0
      - chardet==3.0.4
      - cloudpickle==0.8.1
      - configparser==3.7.4
      - cvxopt==1.2.3
      - decorator==4.4.0
      - defusedxml==0.5.0
      - docutils==0.14
      - doit==0.29.0
      - entrypoints==0.3
      - ephem==3.7.6.0
      - funcsigs==1.0.2
      - h5py==2.9.0
      - idna==2.8
      - imagesize==1.1.0
      - importlib-resources==1.0.2
      - ipaddress==1.0.22
      - ipykernel==4.10.0
      - ipython==5.8.0
      - ipython-genutils==0.2.0
      - ipywidgets==7.4.2
      - jinja2==2.10
      - joblib==0.12.5
      - jsonschema==3.0.1
      - jupyter==1.0.0
      - jupyter-client==5.2.4
      - jupyter-console==5.2.0
      - jupyter-core==4.4.0
      - llvmlite==0.28.0
      - lxml==4.3.3
      - markupsafe==1.1.1
      - mistune==0.8.4
      - mock==2.0.0
      - nbconvert==5.4.1
      - nbformat==4.4.0
      - networkx==2.2
      - notebook==5.7.8
      - numba==0.43.1
      - packaging==19.0
      - pandocfilters==1.4.2
      - pathlib2==2.3.3
      - patsy==0.5.1
      - pbr==5.1.3
      - pexpect==4.6.0
      - pickleshare==0.7.5
      - pkginfo==1.5.0.1
      - plotly==3.7.1
      - prometheus-client==0.6.0
      - prompt-toolkit==1.0.15
      - ptyprocess==0.6.0
      - py4design==0.27
      - pycollada==0.6
      - pygments==2.3.1
      - pyinotify==0.9.6
      - pymc3==3.6
      - pymf==0.1.9
      - pyrsistent==0.14.11
      - pysal==1.14.4.post2
      - pyshp==2.1.0
      - pyyaml==5.1
      - pyzmq==18.0.1
      - qtconsole==4.4.3
      - readme-renderer==24.0
      - requests==2.21.0
      - requests-toolbelt==0.9.1
      - retrying==1.3.3
      - salib==1.2
      - scandir==1.10.0
      - scikit-learn==0.20.3
      - seaborn==0.9.0
      - send2trash==1.5.0
      - simplegeneric==0.8.1
      - snowballstemmer==1.2.1
      - sphinx==1.8.5
      - sphinxcontrib-websupport==1.1.0
      - terminado==0.8.2
      - testpath==0.4.2
      - theano==1.0.4
      - timezonefinder==4.0.1
      - tqdm==4.31.1
      - traitlets==4.3.2
      - twine==1.13.0
      - typing==3.6.6
      - urllib3==1.24.1
      - utm==0.4.2
      - wcwidth==0.1.7
      - webencodings==0.5.1
      - widgetsnbextension==3.4.2
      - xlrd==1.2.0
      - xlwt==1.3.0
      - deap==1.3.0
  </code></pre>