This appears to be a regression of #536

conda version : 4.5.0
conda-build version : 3.8.0
python version : 3.5.5.final.0
platform : win-64

Run a command such as follows:

conda create --yes -n TestEnv1 requests > stdout.txt 2> stderr.txt

Note that all the progress bar output goes into stderr.txt, while the rest goes into stdout.txt, as expected. Here's my stderr.txt:

win_inet_pton 1.0.1: | 0%
win_inet_pton 1.0.1: ########## | 100%

cffi 1.11.5: | 0%
cffi 1.11.5: #######5 | 75%
cffi 1.11.5: #########6 | 96%
cffi 1.11.5: ########## | 100%

pycparser 2.18: | 0%
pycparser 2.18: #######5 | 75%
pycparser 2.18: #########7 | 97%
pycparser 2.18: ########## | 100%

pip 9.0.3: | 0%
pip 9.0.3: #3 | 14%
pip 9.0.3: #####7 | 57%
pip 9.0.3: #######5 | 75%
pip 9.0.3: ########7 | 87%
pip 9.0.3: #########6 | 97%
pip 9.0.3: ########## | 100%

chardet 3.0.4: | 0%
chardet 3.0.4: #######5 | 75%
chardet 3.0.4: #########5 | 95%
chardet 3.0.4: ########## | 100%

six 1.11.0: | 0%
six 1.11.0: ########1 | 82%
six 1.11.0: ########## | 100%

vs2015_runtime 14.0.25420: | 0%
vs2015_runtime 14.0.25420: ###1 | 31%
vs2015_runtime 14.0.25420: #######5 | 75%
vs2015_runtime 14.0.25420: ########5 | 86%
vs2015_runtime 14.0.25420: #########5 | 95%
vs2015_runtime 14.0.25420: ########## | 100%

certifi 2018.1.18: | 0%
certifi 2018.1.18: ########8 | 88%
certifi 2018.1.18: ########## | 100%

openssl 1.0.2o: | 0%
openssl 1.0.2o: 1 | 2%
openssl 1.0.2o: #8 | 18%
openssl 1.0.2o: ###6 | 36%
openssl 1.0.2o: #####4 | 55%
openssl 1.0.2o: #######3 | 73%
openssl 1.0.2o: ########5 | 86%
openssl 1.0.2o: #########5 | 96%
openssl 1.0.2o: ########## | 100%

idna 2.6: | 0%
idna 2.6: #######8 | 79%
idna 2.6: ########## | 100%

asn1crypto 0.24.0: | 0%
asn1crypto 0.24.0: #######5 | 75%
asn1crypto 0.24.0: #########5 | 95%
asn1crypto 0.24.0: ########## | 100%

pysocks 1.6.8: | 0%
pysocks 1.6.8: ########## | 100%

cryptography 2.2.2: | 0%
cryptography 2.2.2: 2 | 2%
cryptography 2.2.2: #######5 | 75%
cryptography 2.2.2: #########3 | 93%
cryptography 2.2.2: ########## | 100%

urllib3 1.22: | 0%
urllib3 1.22: #######5 | 75%
urllib3 1.22: #########5 | 96%
urllib3 1.22: ########## | 100%

requests 2.18.4: | 0%
requests 2.18.4: #######7 | 77%
requests 2.18.4: ########## | 100%

python 3.6.5: | 0%
python 3.6.5: 2 | 3%
python 3.6.5: 7 | 7%
python 3.6.5: #2 | 12%
python 3.6.5: #6 | 17%
python 3.6.5: ##1 | 21%
python 3.6.5: ##5 | 26%
python 3.6.5: ### | 30%
python 3.6.5: ###4 | 35%
python 3.6.5: ###9 | 40%
python 3.6.5: ####4 | 44%
python 3.6.5: ####8 | 48%
python 3.6.5: #####2 | 53%
python 3.6.5: #####7 | 58%
python 3.6.5: ######2 | 62%
python 3.6.5: ######6 | 67%
python 3.6.5: #######1 | 71%
python 3.6.5: #######5 | 76%
python 3.6.5: #######8 | 79%
python 3.6.5: ########1 | 81%
python 3.6.5: ########2 | 83%
python 3.6.5: ########4 | 84%
python 3.6.5: ########5 | 85%
python 3.6.5: ########5 | 86%
python 3.6.5: ########6 | 87%
python 3.6.5: ########7 | 87%
python 3.6.5: ########7 | 88%
python 3.6.5: ########8 | 88%
python 3.6.5: ########8 | 89%
python 3.6.5: ########8 | 89%
python 3.6.5: ########9 | 89%
python 3.6.5: ########9 | 90%
python 3.6.5: ########9 | 90%
python 3.6.5: ######### | 90%
python 3.6.5: ######### | 91%
python 3.6.5: ######### | 91%
python 3.6.5: #########1 | 91%
python 3.6.5: #########1 | 92%
python 3.6.5: #########1 | 92%
python 3.6.5: #########2 | 92%
python 3.6.5: #########2 | 93%
python 3.6.5: #########2 | 93%
python 3.6.5: #########3 | 93%
python 3.6.5: #########3 | 93%
python 3.6.5: #########3 | 94%
python 3.6.5: #########4 | 94%
python 3.6.5: #########4 | 94%
python 3.6.5: #########4 | 95%
python 3.6.5: #########4 | 95%
python 3.6.5: #########5 | 95%
python 3.6.5: #########5 | 95%
python 3.6.5: #########5 | 96%
python 3.6.5: #########6 | 96%
python 3.6.5: #########6 | 96%
python 3.6.5: #########6 | 97%
python 3.6.5: #########6 | 97%
python 3.6.5: #########7 | 97%
python 3.6.5: #########7 | 97%
python 3.6.5: #########7 | 98%
python 3.6.5: #########7 | 98%
python 3.6.5: #########8 | 98%
python 3.6.5: #########8 | 98%
python 3.6.5: #########8 | 99%
python 3.6.5: #########8 | 99%
python 3.6.5: #########8 | 99%
python 3.6.5: #########9 | 99%
python 3.6.5: #########9 | 99%
python 3.6.5: #########9 | 100%
python 3.6.5: #########9 | 100%
python 3.6.5: #########9 | 100%
python 3.6.5: #########9 | 100%
python 3.6.5: ########## | 100%

pyopenssl 17.5.0: | 0%
pyopenssl 17.5.0: ########5 | 86%
pyopenssl 17.5.0: ########## | 100%

setuptools 39.0.1: | 0%
setuptools 39.0.1: #######5 | 75%
setuptools 39.0.1: ########9 | 89%
setuptools 39.0.1: ########## | 100%

ca-certificates 2018.03.07: | 0%
ca-certificates 2018.03.07: #######6 | 77%
ca-certificates 2018.03.07: ########## | 100%

wincertstore 0.2: | 0%
wincertstore 0.2: ########## | 100%

wheel 0.31.0: | 0%
wheel 0.31.0: ########5 | 86%
wheel 0.31.0: ########## | 100%

vc 14: | 0%
vc 14: ########## | 100%