Merge pull request #109 from nmfs-opensci/eeholmes-patch-2

fix apt.txt in child

appendix

@@ -77,7 +77,7 @@ ONBUILD RUN echo "Checking for 'apt.txt'..." \
         ; [ -d binder ] && cd binder \
         ; [ -d .binder ] && cd .binder \
         ; if test -f "apt.txt" ; then \
-        package_list=$(grep -v '^\s*#' ${REPO_DIR}/apt-extras.txt | grep -v '^\s*$' | sed 's/\r//g; s/#.*//; s/^[[:space:]]*//; s/[[:space:]]*$//' | awk '{$1=$1};1') \
+        package_list=$(grep -v '^\s*#' apt.txt | grep -v '^\s*$' | sed 's/\r//g; s/#.*//; s/^[[:space:]]*//; s/[[:space:]]*$//' | awk '{$1=$1};1') \
         && apt-get update --fix-missing > /dev/null \
         && apt-get install --yes --no-install-recommends $package_list \
         && apt-get autoremove --purge \