I will compile form designed by qt designer in eric6, but show "Could not start pyuic5, Ensure that it is in the search path." But actually the PATH of  pyuic5.exe has been in the system PATH, and also the pyuic5.exe can be run by typing pyuic5 in the cmd of window7 .
The envirement is python3.5+qt5.7+pyqt5.7+eric6.
Why I could not compile form in eric6? How can fix the error?
Had the exact same issue. Looks like Eric wants pyuic5.bat (somewhere in the path)
I created such a batch file with the following contents, and it worked

@"pyuic5.exe" %1 %2 %3 %4 %5 %6 %7 %8 %9

PS: In my setup these files are both located in a folder:

C:\Python35-32\Scripts
Compile form in eric6, but show "Could not start pyuic5, Ensure that it is in the search path."