[CI] use conda < 4.3.14

to avoid signal_handler bug seen on travis
    conda/conda#5033

[skip appveyor]

.travis.yml

@@ -34,7 +34,7 @@ matrix:
       env: TOXENV=docs_linkcheck
     # check that conda build/install works
     - os: linux
-      python: '3.4'
+      python: '3.6'
       env: TOXENV=condarecipe
     # linux, various python and notebook versions
     - os: linux
@@ -115,15 +115,19 @@ before_install:
   - 'if [[ ${TOXENV} == "condarecipe" ]]; then hash -r; fi'
   - 'if [[ ${TOXENV} == "condarecipe" ]]; then conda config --set always_yes yes --set changeps1 no; fi'
   - 'if [[ ${TOXENV} == "condarecipe" ]]; then conda info -a; fi  # Useful for debugging any issues with conda'
-  # conda 4.3.14 & conda-build 2.1.6,2.1.7 seem to fail with signals TypError on travis.
+
+  # conda >4.3.13 seems to fail with TypeError thrown by sginal_handler on travis.
+  # for further details, see
+  #     https://github.com/conda/conda/issues/5033
   # conda's auto-update strategy also means that installing or updating anything else will cause
-  # conda to attempt to update itself.
+  # conda to attempt to update itself, so we may need to re-specify conda version at each install/update step
   # Thus instead of running
   #    conda update conda
   # we install conda & conda-build together, specifying the versions that we
   # wish to avoid
-  - 'if [[ ${TOXENV} == "condarecipe" ]]; then conda install "conda!=4.3.14" "conda-build!=2.1.6,!=2.1.7"; fi'
+  - 'if [[ ${TOXENV} == "condarecipe" ]]; then conda install "conda<4.3.14" "conda-build"; fi'
   - 'if [[ ${TOXENV} == "condarecipe" ]]; then conda info -a; fi  # Useful for debugging any issues with conda'
+  - 'if [[ ${TOXENV} == "condarecipe" ]]; then conda config --append channels conda-forge; fi  # add conda-forge channel at lower priority than defaults'
   - 'if [[ ${TOXENV} == "condarecipe" ]]; then git fetch --unshallow; fi'
 install:
   - pip install tox

tox.ini

@@ -172,6 +172,5 @@ deps =
 whitelist_externals =
     conda
 commands =
-    conda config --prepend channels conda-forge  # add conda-forge channel at lower priority than defaults
     conda build conda.recipe
     conda install --use-local jupyter_contrib_nbextensions