sudo port -t install opencv
--->  Computing dependencies for opencv
--->  Fetching archive for opencv
--->  Attempting to fetch opencv-3.4.1_2.darwin_13.x86_64.tbz2 from https://packages.macports.org/opencv
--->  Attempting to fetch opencv-3.4.1_2.darwin_13.x86_64.tbz2 from http://ywg.ca.packages.macports.org/mirror/macports/packages/opencv
--->  Attempting to fetch opencv-3.4.1_2.darwin_13.x86_64.tbz2 from http://sea.us.packages.macports.org/macports/packages/opencv
--->  Fetching distfiles for opencv
--->  Verifying checksums for opencv
--->  Extracting opencv
--->  Applying patches to opencv
--->  Configuring opencv
Warning: The following existing files were hidden from the build system by trace mode:
  /opt
  /opt/local/bin/gmake
  /opt/local/bin/install_name_tool
  /usr/X11R6
Warning: The following files inside the MacPorts prefix not installed by a port were accessed:
  /opt/local/bin/daemondo
  /opt/local/bin/port
  /opt/local/bin/port-tclsh
  /opt/local/bin/portf
  /opt/local/bin/portindex
  /opt/local/bin/portmirror
  /opt/local/include/.turd_MacPorts
  /opt/local/libexec/macports/bin/tclsh8.5
  /opt/local/man
  /opt/local/sbin/.turd_MacPorts
--->  Building opencv
Warning: The following existing files were hidden from the build system by trace mode:
  /opt
  /opt/local/include/GL/glx.h
Error: Failed to build opencv: command execution failed
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_graphics_opencv/opencv/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets to report a bug.
Error: Processing of port opencv failed