env:digispark-tiny, env:attiny45: uploading does not do anything

[Flummy]

PlatformIO, version 3.1.0 on Ubuntu 16.04.1 x86_64

Using a breadboarded ATtiny45, "Blink" example sketch to be programmed with a mySmartUSBlight on /dev/mysmartusb1 (symlink to /dev/ttyUSB1) and platformio.ini.txt

The Blink sketch is built successfully, but the upload using programmer claims "=== [SUCCESS]" without even calling avrdude:

$ pio run --environment digispark-tiny --target=program
Looking for upload port...
Programming .pioenvs/digispark-tiny/firmware.hex
=== [SUCCESS]

$ pio run --verbose --environment digispark-tiny --target=program --upload-port /dev/mysmartusb1
BeforeUpload(["program"], [".pioenvs/digispark-tiny/firmware.hex"])
=== [SUCCESS]

The usual "avrdude: AVR device initialized and ready to accept instructions" output is not displayed.

• I (believe I) successfully uploaded a sketch to an ATtiny45 using a unknown version of platformio today
• Then I updated PlatformIO, PlatformIO IDE and Atom
• Now avrdude is never called when executing pio run --environment digispark-tiny --target=program:
  pio-attiny-strace.txt

I also exited atom, removed $HOME/.platformio and tried again with the same outcome.
My micronucleus binary seems to be ELF 64 bit.
Edit: Uploading using the IDE menu functions "Upload using Programmer" and "Upload" had the same result.